Standards and standardization in mastocytosis: Consensus Statements on Diagnostics, Treatment Recommendations and Response Criteria

European Journal of Clinical Investigation

(2007)

37

, 435–453

© 2007 The Authors. Journal Compilation © 2007 Blackwell Publishing Ltd

Blackwell Publishing Ltd

Review

Standards and standardization in mastocytosis: Consensus Statements on Diagnostics, Treatment Recommendations and Response Criteria

P. Valent, C. Akin, L. Escribano, M. Födinger, K. Hartmann, K. Brockow, M. Castells, W. R. Sperr, H. C. Kluin-Nelemans, N. A. T. Hamdy, O. Lortholary, J. Robyn, J. van Doormaal, K. Sotlar, A. W. Hauswirth, M. Arock, O. Hermine, A. Hellmann, M. Triggiani, M. Niedoszytko, L. B. Schwartz, A. Orfao, H.-P. Horny, D. D. Metcalfe

Abstract

Although a classification for mastocytosis and diagnostic criteria are available, there remainsa need to define standards for the application of diagnostic tests, clinical evaluations, andtreatment responses. To address these demands, leading experts discussed current issues andstandards in mastocytosis in a Working Conference. The present article provides the resultingoutcome with consensus statements, which focus on the appropriate application of clinicaland laboratory tests, patient selection for interventional therapy, and the selection ofappropriate drugs. In addition, treatment response criteria for the various clinical conditions,disease-specific symptoms, and specific pathologies are provided. Resulting recommendationsand algorithms should greatly facilitate the management of patients with mastocytosis inclinical practice, selection of patients for therapies, and the conduct of clinical trials.

Keywords

Criteria, mastocytosis, patient selection, standardization, targeted drugs

Eur J Clin Invest 2007; 37 (6): 435–453

Introduction

Mastocytosis is a heterogeneous disease characterized byan accumulation of mast cells (MC) in one or more organs

[1–10]. The clinical course ranges from ‘asymptomatic’ withnormal life expectancy to ‘highly aggressive’ [1–12]. In addi-tion, patients often suffer from mediator-related symptoms[3–7]. The WHO-classification defines 7 disease-variants:

Department of Internal Medicine I, Division of Haematology & Haemostaseology, Medical University of Vienna, Vienna, Austria (P. Valent, W.R. Sperr, A.W. Hauswirth), Department of Internal Medicine, Division of Allergy and Immunology, University of Michigan, Ann Arbor, MI, USA (C. Akin), Servicio de Hematologia, Unidad de Mastocitosis, Hospital Ramón y Cajal, Madrid, Spain (L. Escribano), Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, Austria (M. Födinger), Clinic and Polyclinic of Dermatology & Venerology, University of Cologne, Germany (K. Hartmann), Department of Dermatology and Allergy Biederstein, Technical University of Munich, Germany (K. Brockow), Division of Rheumatology, Immunology & Allergy, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA (M. Castells), Department of Haematology, University Medical Centre Groningen, Groningen, the Netherlands (H.C. Kluin-Nelemans), Department of Endocrinology & Metabolic Diseases, Leiden University Medical Centre, Leiden, the Netherlands (N.A.T. Hamdy), Université Paris V, Hôpital Necker-Enfants Malades, Service des Maladies Infectieuses (O. Lortholary), Haematology Branch, National Heart Lung and Blood Institute, NIH Bethesda, MD, USA (J. Robyn), Department of Allergology, University Hospital Groningen, Groningen, the Netherlands (J. van Doormaal), Institute of Pathology, University of Tübingen, Germany (K. Sotlar), LBPA CNRS UMR 8113, Ecole Normale Supérieure de Cachan, Cachan, France (M. Arock), Department of Adult Haematology, and CNRS UMR 8147, Univesité René Descarte, Assistance Publique Hôpitaux de Paris, Hôpital Necker, Paris, France (O. Hermine), Department of Haematology, Medical University of Gdansk, Poland (A. Hellmann), Facolta Medicina e Chirurgia, Cattedra di Immunologia Clinica e Allergologia Universitá degli studi di Napoli Federico II, Naples, Italy (M. Triggiani), Department of Allergology, Medical University of Gdansk, Poland (M. Niedoszytko), Department of Internal Medicine, Division of Rheumatology, Allergy & Immunology, Virginia Commonwealth University, Richmond, VA, USA (L.B. Schwartz), Servicio Central de Citometria, Centro de Investigacion del Cancer and Department of Medicine, University of Salamanca, Spain (A. Orfao), Institute of Pathology, University of Schleswig-Holstein, Campus Lübeck, Lübeck, Germany (H.-P. Horny), Laboratory of Allergic Diseases, NIAID, NIH, Bethesda, MD, USA (D.D. Metcalfe).

a

This article is dedicated to the achievements of Professor Reza M. Parwaresch who passed away shortly before the start of the Working Conference.

Correspondence to: Peter Valent, M.D., Department of Internal Medicine I, Division of Haematology & Haemostaseology, Medical University of Vienna, Waehringer Guertel 18–20, A-1090 Vienna, Austria. Tel.: +43 140400-5488, -6085, -6086; fax: +43 140400 4030; e-mail: [email protected]

Received 1 December 2006; Accepted 13 February 2007

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cutaneous mastocytosis (CM), indolent systemic masto-cytosis (ISM), SM with an associated clonal haematologicalnon-MC-lineage disease (SM-AHNMD), aggressive SM(ASM), MC leukaemia (MCL, leukaemic SM-variant), MCsarcoma (MCS), and extracutaneous mastocytoma [9,10].SM is defined by major and minor SM-criteria [9,10]. If atleast one major and one minor or at least three minorSM-criteria are fulfilled, the diagnosis is SM [9–11]. Tosub-classify SM, criteria defining the MC-burden, involve-ment of non-MC-lineages, and aggressiveness of disease(C-Findings), are applied (Fig. 1a) [9–11]. In addition, athorough haematological evaluation is performed to revealor exclude an AHNMD [9,10].

Despite the availability of diagnostic criteria, thereremains a need to define standards for evaluations and tests,for patient selection, for the appropriate selection of drugs,and for response criteria, which is important because of thecomplexity of the disease and because of rapidly emergingnew pharmaceutical agents [12,13].

To address these demands, the Year-2005 Working Con-ference on Mastocytosis was convened. Disease-specificissues were discussed extensively before, during, and afterthis conference (May 2005 to April 2006; Conference-Time:November 3–6, 2005) until consensus was reached. Result-ing consensus recommendations and proposed diagnosticand therapeutic algorithms are reported herein.

Cutaneous disease involvement

In many patients, the first sign of disease is a typical exan-thema that is usually maculopapular and intensifies uponrubbing (Darier’s sign) [14–16]. Unfortunately, in adults,the rash is frequently misdiagnosed as CM, although, onceapplied, SM criteria reveal SM in most cases. Therefore, theconsensus is to apply SM criteria in all adult patients, andto differentiate distinctively between the pre-diagnosticcheckpoint ‘mastocytosis in the skin’ (MIS) and the finaldiagnosis, which has to be based on SM-related criteria, andthen is either CM or SM (Fig. 1b).

Proposed criteria for MIS

MIS is evaluated by inspection of lesional skin (plus photo-graphy), a skin biopsy with tryptase immunohistochemistry(IHC), and

KIT

mutation analysis [14–17]. MIS is thusdefined by a typical exanthema (major MIS criterion) andone or two of the following minor MIS criteria: (i) mono-morphic MC infiltrate that either consists of large aggregatesof tryptase-positive MC (> 15 cells/cluster) or scattered MCexceeding 20 cells per microscopic high power field (

×

40);(ii) detection of a

KIT

mutation at codon 816 in lesionalskin. Minor MIS-criteria are applied in a step-wise fashion.Thus, if the histology (step-1) is questionable for any reason(e.g. polymorphic cell-infiltrate, low MC numbers), MIScan still be diagnosed provided that a

KIT

mutation atcodon 816 (step-2) is detectable in affected skin (Fig. 1b).If the macroscopic picture is in question, the presence ofthe Darier’s sign may help in reaching the conclusion the

rash is typical. In such cases, other skin diseases must beexcluded, and lesional skin examined for

KIT

-816-mutations(Fig. 1b).

Approach to final diagnosis: CM or SM

From the checkpoint MIS, the algorithm leads to twofinal diagnoses, CM or SM (Fig. 1c). The term ‘CM withsystemic involvement’ is obsolete and thus should beavoided. Most paediatric patients suffer from CM, whereasadults usually have SM [9,10,14–16]. Therefore, in adults,a bone marrow examination (BME) is always performedeven if the serum tryptase is normal. In children withtryptase < 20 ng mL

−

1

, the diagnosis of CM may bedecided upon without BME, unless other signs of SMare present. If the serum tryptase is 20–100 ng mL

−

1

inchildren without other signs of SM, the provisional diag-nosis ‘MIS’ can be established and monitored until puberty(Fig. 1c). If MIS remains present after puberty, a BMEis performed. If the baseline tryptase level exceeds100 ng mL

−

1

, a BME should be considered regardless of age(Fig. 1c).

Subvariants of CM

CM is divided into maculopapular CM (MPCM = urticariapigmentosa, UP), diffuse cutaneous mastocytosis (DCM),and solitary mastocytoma of skin [9,10,14–20]. Clinicalfeatures of CM-variants are well defined [14–20]. Impor-tantly, the skin lesions in MPCM may present with multiplemacroscopic features and may change over time [14–16].Also, sub-variants of CM may coexist at different sites inone patient. In such cases, the final diagnosis should bebased on the predominant subtype.

Grading of MIS and natural course

The extent of MIS is documented by photography andreported as estimated percent of body surface, taking intoaccount overall involvement of the skin and the percent ofinvolved skin in local areas (e.g. 50% body surface and 50%local, equals 25%) [21].

MIS-specific symptoms to be graded include pruritus,flushing, and blistering. The following grading system isproposed: 0 (no symptoms), 1 (mild, infrequent, no therapyrequired), 2 (mild/moderate, frequent, kept under controlwith therapy), 3 (severe, frequent, difficult to control), and4 (requiring hospitalization = severe adverse event, SAE)(Table 1a). The frequency of grade-4-events is alsoreported: A (< 1/year), B (> 1/year and < 1/month), andC (> 1/month).

In most children with CM, skin lesions disappear at orshortly after puberty [14–16,22]. Less frequently, MISpersists – these patients are often diagnosed with SM inadulthood [14]. In adults, skin lesions remain stable orincrease with time. Rarely, the lesions decrease spontane-ously [14–16,23]. This is of importance as aggressivevariants of SM or MCL may present without MIS. Thepotential of spontaneous regression should also be

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Figure 1 (a) Master algorithm for the delineation of sub-variants of systemic mastocytosis (SM). In patients in whom at least one major and one minor or at least three minor SM criteria are detected, the diagnosis SM is established. Major SM criterion is the multifocal dense infiltrate of mast cells (MC) in the bone marrow or in other extracutaneous organ(s) (> 15 MC per aggregate) detected by tryptase-immunohistochemistry (IHC). Minor SM criteria are: (i) MC show an abnormal morphology = atypical MC type I (> 25%) in bone marrow smears, or are spindle-shaped cells (> 25%) in compact infiltrates in extracutaneous organ(s); (ii) a KIT mutation at codon 816 in extracutaneous organ(s) (bone marrow is the recommended organ for screening) is detectable; (iii) KIT+ MC in the bone marrow or in another extracutaneous organ express CD2 and/or CD25; and (iv) serum tryptase > 20 ng mL−1 (does not count in patients who have AHNMD-type disease). Using criteria defining the spread of disease (B-Findings) and the aggressiveness of the mast cell infiltrate (= grading criteria = C-Findings) as well as WHO criteria for the definition of non MC haematopoietic neoplasms, the (sub)variant of SM and thus the final diagnosis, is established. In SM-AHNMD, the SM component of the disease should be determined, i.e. in patients with AHNMD, B-Findings and C-Findings should be applied in the same way as in those without AHNMD (arrow, *). (b) Checkpoint ‘mastocytosis in the skin’ (MIS): diagnostic algorithm. If one major and one (or two) minor ‘skin-criteria’ are fulfilled, the diagnosis ‘mastocytosis of the skin’ is established. If the histology is questionable, the demonstration of a KIT mutation at codon 816 (second minor criterion, step 2) is applied and may provide evidence for the presence of a primary mast cell disease = mastocytosis. In case of an atypical rash, the Darier’s sign may be demonstrated, and other skin diseases excluded by laboratory studies as well as by histological examination. In these cases, demonstration of a KIT mutation at codon 816 is confirmatory for MIS. Therefore, such studies should be performed, if possible (dotted line).

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(c) Search for SM in patients with ‘mastocytosis in the skin’ (MIS): algorithm. The two paths result from the known differences in the frequency of occurrence of SM in adults (frequent) and in children (unusual event). A complete staging with bone marrow examination and application of all SM criteria is performed in (i) all adult patients and (ii) all children in whom the serum tryptase is high and/or constantly increasing or/and other signs of a systemic disease are found (*): cytopenia, leukocytosis, abnormal differential count, hepatomegaly, splenomegaly, or lymphadenopathy. All children with MIS (or established cutaneous mastocytosis) should be monitored (serum tryptase, signs of systemic disease) until adolescence. The decision to perform a bone marrow biopsy after puberty depends on the presence (persistence) of skin lesions, the serum tryptase level, and signs of internal organ involvement. (d) Algorithm for patients exhibiting the major SM-criterion in tryptase-stained bone marrow sections – Pathology Algorithm ‘A’. In most cases, the multifocal diagnostic tryptase-positive mast cell infiltrates are composed of or are even dominated by spindle-shaped mast cells – in these cases, the final diagnosis is SM. In a few patients, however, a majority or even vast majority of all tryptase-stained mast cells in these infiltrates are round – in the latter patients, the checkpoint ‘TROCI’ is established. In these patients, the identity of neoplastic cells in TROCI infiltrates has to be determined by immunohistochemistry and/or flow cytometry. Co-expression of KIT and CD25 in TROCI cells is confirmatory for the presence of neoplastic mast cells and thus the diagnosis SM. If CD25 is not expressed by IHC and flow cytometry, but the cells are clearly mast cells, the final diagnosis may be reactive mast cell hyperplasia. In patients with KIT mutations, MMUS (monoclonal mast cells with undetermined significance) or MMAS (monoclonal mast cell activation syndrome) may be diagnosed. *In these cases, follow up may reveal one minor SM criterion (e.g. increase in serum tryptase level to > 20 ng mL−1) – which then leads to the diagnosis of ‘well differentiated systemic mastocytosis’. (e) Algorithm for patients with sub-diagnostic infiltrates of tryptase-positive cells in bone marrow biopsy sections – Pathology Algorithm ‘B’. The primary checkpoints (unifocal infiltrate, multifocal small-sized infiltrate, occult or distorted infiltrates in SM-AHNMD) are only detected in tryptase-stained bone marrow biopsy sections. In each case, the pathologist will review for minor SM criteria as a first step. In case of questionable material, the pathologist may request a second bone marrow biopsy. The final diagnosis depends on the number of minor SM-criteria, the presence of ‘mastocytosis in the skin’, and the presence of an AHNMD. In all cases, a follow up with monitoring of serum tryptase is recommended. In those with an AHNMD, the pathologist will also request another bone marrow biopsy at the time of therapy-induced remission to document or exclude occult mastocytosis (**). MMUS: monoclonal mast cells with undetermined significance; MMAS: monoclonal mast cell activation syndrome.

Figure 1 Continued


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Table 1a Grading of skin-specific symptoms in patients with mastocytosis*

Grade Definition

0 = no symptoms prophylaxis†, but requires no other therapy‡

1 = mild, infrequent prophylaxis ± as needed therapy2 = mild/moderate,

frequentrequires and can be controlled by daily therapy§

3 = severe, frequent suboptimal or unsatisfactory control with daily and combination therapy§

4 = severe adverse event¶ requires immediate therapy and hospitalization

*Pruritus, flushing, blistering, bullae formation, †all patients with mastocytosis are advised to avoid precipitating factors and events – for most of them, prophylactic antihistamines (H1 and H2 histamine receptor antagonists) are recommended, ‡unless the patient is focused on the cosmetic consequences of the disease or suffers from systemic mediator-related symptoms, §despite avoidance of precipitating factors, ¶the frequency of severe adverse events should also be reported: 4A: < 1 year−1; 4B: > 1 year−1 and < 1 month−1; 4C: > 1 month−1.

Table 1b Therapeutic options for cutaneous symptoms in patients with mastocytosis

Symptom (variant)

Proposed therapies

First line, grade 1–2* First line, grade 3* and Second line, grade 2*

Pruritus (all variants) H1 antihistamines UV irradiation, PUVAtopical cromolyn sodium H1 + H2 antihistamines,

leukotriene antagonists, glucocorticoidsFlushing (all variants) H1 antihistamines H1 + H2 antihistamines

leukotriene antagonists UV irradiation, PUVABlistering (all variants) Local therapy H1 + H2 antihistamines

H1 antihistamines systemic glucocorticoidstopical cromolyn sodium

Bullae (usually DCM and mastocytomas)

Local care, dressing H1 + H2 antihistamines systemic glucocorticoids topical cromolyn sodium

Mastocytoma lesion with symptoms or increasing size

Local immuno-suppressants, local UV irradiation and psoralen bath or cream

Excision

*Grade 0 patients are usually not treated unless they suffer from significant non-organic symptoms or systemic mediator related symptoms. Grade 4 patients may be hospitalized and treated with antimediator-type drugs, other stabilizing agents, and local therapies depending on the overall condition and local skin problems.

DCM, diffuse cutaneous mastocytosis.

Table 1c Skin involvement and skin-specific symptoms in mastocytosis: proposed response criteria*

(1)

(2)

Regression regarding the extent of disease in the skin (in percent) Definition

Complete regression (CR) all skin lesions disappeared→ Continuous CR (CCR)† continuous disappearance

of lesions†Major regression (MR) > 50% of all lesions disappeared‡Partial regression (PR) 10–50% of lesions disappearedNo regression (NR) < 10% of lesions disappeared

Responses regarding the severity of skin-specific symptoms Definition

Complete regression (CR) all symptoms disappeared→ Continuous CR (CCR)† constantly asymptomatic†Major regression (MR) > 50% of all symptoms

disappeared or/and decrease in frequency of severe (grade 4)events from B to A or from C to B

Partial regression (PR) 10–50% of symptoms disappearedNo regression (NR) < 10% of symptoms disappeared

*The best result is recorded regardless of the duration of the regression – exception: in patients with grade 4B or 4C skin disease (see Table 5), CR or MR can only be recorded when the frequency of severe attacks did not increase over time, which requires a careful follow-up of the patient.

†In patients with CR, the remission status is carefully examined over time. If no further attacks are recorded after 2 years of observation, CR becomes CCR = continuous complete regression.

‡Example: 10% of the skin was involved with urticaria pigmentosa (UP) before therapy, but only 3% (less than 5%) of the skin surface is involved after therapy = MR (major regression).

considered when interpreting treatment responses. Inaddition, skin lesions fade with exposure to UV-light, whichmay result from changes in pigmentation rather than fromregression of lesions.

Treatment of MIS and proposed response criteria

All patients are advised to avoid (as possible) all agents andsituations that provoke a reaction. Antihistamines may beprescribed as prophylaxis. Otherwise, ‘grade 0 disease’is not treated unless the patient is focused on cosmetic

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consequences. In symptomatic patients, topical or/andsystemic therapy is selected as outlined in Table 1b[24–28].

Based on the percent of affected skin before and aftertherapy (photography), the following responses are scored:complete regression, CR (complete disappearance of MIS),major regression, MR (reduction by more than 50%),partial regression, PR (10–50%), and no regression, NR(< 10%) (Table 1c).

Changes in MIS-specific symptoms are also determined.Again, a CR, MR, PR, or NR is recorded (Table 1c). Suchevaluation is subjective and should be performed using apatient-diary or questionnaire. In patients with grade 4B or4C, CR or MR are only accepted when the frequency ofattacks did not increase (Table 1c).

SM without MIS

SM without MIS is a challenge for the physician. Thepre-diagnostic interval may be substantial. Absence ofMIS is often seen in ASM and MCL [1,2,9,10]. However,not all patients who lack skin lesions have aggressive dis-ease. Rather, many of them have (isolated) bone marrowmastocytosis (BMM), a subcategory of ISM with lowburden of MC, low serum tryptase, and a good prognosis[9,10].

A number of clinical conditions may lead to the suspicionof BMM, such as unexplained anaphylaxis, unexplainedosteopathy (e.g. osteoporosis of unknown aetiology),unexplained neurological or constitutional symptoms,unexplained ulcerative intestinal disease or chronic diar-rhoea, or an unexplained ‘endocrinological syndrome’[29–33].

The bone marrow in mastocytosis: proposed standards and algorithms

A thorough histological, immunohistochemical, andmorphologic BME remains an important feature in thediagnostic work-up in suspected SM [9,10,34–41].

Histology and immunohistochemistry (IHC)

The trephine biopsy-specimen should be of adequate length(

≥

2 cm), fixed in neutral formalin, decalcified in EDTA,and embedded in paraffin-wax.

Tryptase is the standard IHC-stain recommended forMC-detection and reporting of MC-infiltration (percentageof cellular marrow-space) [35–38]. Antibodies against KIT/CD117 and CD25 should also be employed [35,38,39].The IHC technique for these markers has to be establishedfor MC-detection in SM in each laboratory. A CD25-stainingprotocol should qualify as a diagnostic test if (a) in a givenpopulation of patients with typical ISM, the antibodyproduces a positive stain in MC in > 80% of all cases, and(b) the internal positive-control (lymphocyte-subset) andnegative-control show expected results.

In most SM-patients, tryptase-positive infiltrates arecomposed of spindle-shaped MC [34–41]. In these patients,SM can be diagnosed without additional tests (major +minor SM-criterion fulfilled). This is not the case in patientswith a tryptase-positive round cell-infiltrate (definition ofTROCI: > 95% round tryptase-positive cells; < 5% spindle-shaped cells); (Fig. 1d) [42]. In these patients, the applica-tion of additional IHC-markers (CD34, CD117, CD25) isstandard, as basophils and sometimes blast cells (both areround cells) also express some tryptase (Table 2a) [38,42–46]. Co-expression of KIT and CD25 in TROCI-cells ishighly suggestive of SM (CD25 as minor SM criterion)(Fig. 1d) [42]. If KIT-positive MC in TROCI-lesions areCD25-negative, MC-hyperplasia has to be considered[47,48].

Other decision-points in the histology-algorithm includethe isolated MC-infiltrate and the multifocal small-sizedMC-aggregate (< 15 MC/aggregate) (Fig. 1e). In bothinstances, the major SM-criterion is missing, so that it iscritical to consider minor SM-criteria. If these criteria show‘sub-diagnostic’ results (

n

< 3), the haematopathologistmay request a repeat BME [49]. If all studies remain ‘sub-diagnostic’ in a patient with MIS, the final diagnosis is CM(Fig. 1e). In those without MIS, the diagnosis may then be‘reactive MC-hyperplasia’ (no clonal MC found) (Fig. 1e).If MC are found to be monoclonal (e.g. KIT D816V-positive)and mediator-related symptoms are recorded, the proposalis to term the condition ‘monoclonal MC activation syn-drome’ (MMAS).

Another situation is ‘occult SM’ [50–53]. Here, acoexisting AHNMD provides the predominant cell popu-lation, whereas the SM-component is masked by theAHNMD (Fig. 1e). Such patients are often misdiagnosedwith KIT-D816V-positive leukaemia [63,64]. Therefore, werecommend a BME with histology and IHC in all leukaemicpatients with a

KIT

mutation at codon 816. If no SM isdetected, these patients should again be examined for SMcriteria after successful cytoreductive (chemo)therapy toexclude or reveal (occult) SM [50].

The bone marrow smear

Wright-Giemsa is the standard-stain for MC-detectionand enumeration in bone marrow smears [9,10,54]. It isstandard that MC are counted (percent of nucleatedcells) at considerable distance from marrow particles[9,10,54]. An increase in MC to

≥

5% suggests an un-favourable prognosis [54]. If

≥

20% of cells in bone marrowsmears are MC, the diagnosis is MCL, and the prognosisis grave [9,10,54]. The morphology of MC is recorded usingpublished criteria for morphological grading (Table 2b)[54]. The non-MC-compartment should also be examined[9,10,54–56]: Mild dysplasia is found in most patientswith SM [55]. If dysplasia is prominent, the patientshould be examined for additional signs of smoulderingSM (SSM) [56] or an associated myelodysplastic syn-drome (MDS). Other relevant findings include eosi-nophilia, basophilia, or an increase in blasts (see alsoSM-AHNMD).


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Follow-up examinations

The burden of neoplastic MC (and serum tryptase) remainsremarkably stable over years in most patients with ISM(even in most with SSM). In these patients, no repeatedBME is required. However, a BME is warranted if thereis evidence of disease progression (e.g. increase in serumtryptase). In addition, the marrow is examined before andafter therapy with cytoreductive or targeted drugs. The mostimportant follow up parameter is tryptase IHC to evaluateMC-infiltration [11,37]. During treatment with cytoreduc-tive agents or targeted drugs, both the serum tryptase

and marrow MC-infiltration may decrease. Respectiveresponse criteria are available [11] and should be appliedin all cases.

Flow cytometry: proposed standards and markers

In most patients with SM, neoplastic MC aberrantly expressCD25 with or without CD2 [9,10,57–59]. Guidelines forthe phenotypic analysis of MC in SM have been publishedby the Spanish mastocytosis-network [59]. These guidelinesare recommended as a global standard.

Table 2a TROCI: Phenotype of affected cells and differential diagnosis in mastocytosis

Table 2b Progenitors and mast cells detectable in the bone marrow smear in patients with systemic mastocytosis (SM): morphologial criteria and clinical significance*

Marker/antibody Reactivity of TROCI cells with antibodies against leukocyte differentiation antigens by IHC or flow cytometry

CD34 – – +/– +KIT/CD117 + – or –/+* +/– +/–Tryptase + +/– + – or –/+†Chymase +/– – –/+ –2D7 – + – –BB1 – + – –CD25 +/– ‡ –/+§ +/– –

Cell type mast cell basophil metachromatic blast myeloblast

Differential SM/MCL‡ CML, BL, MML, MCL AML, MDSDiagnoses MML, WDSM‡ AHNMD SM, AHNMD AHNMD

Abbreviations: TROCI, tryptase+ round cell infiltrate; IHC, immunohistochemistry; SM, systemic mastocytosis; MCL, mast cell leukaemia; MML, myelomastocytic leukaemia; WDSM, well differentiated systemic mastocytosis; CML, chronic myeloid leukaemia; BL, basophilic leukaemia; AML, acute myeloid leukaemia; MDS, myelodysplastic syndrome; AHNMD, associated haematological clonal non-mast cell lineage disease; *Immature basophils may express low amounts of KIT; †In about 40% of AML cases, blast cells express low amounts of tryptase; ‡Whereas mast cells in SM and MCL usually are CD25+, mast cells in MML and WDSM typically are CD25−. §Basophils express low amounts of CD25 that are detectable by flow cytometry, but are less well detectable by IHC.

Score: +, clearly expressed in most cells; +/– expressed in a subpopulation; –/+, only a few cells are weakly positive; –, not reactive.

Cell type Major criteria* Clinical significance

Non-metachromatic blast (myeloblast)

blast-criteria, no metachromatic granules

ask for AHNMD and dysplasia; (> 5%, > 20%, MDS/AML; → diagnosis SM-MDS, SM-AML)

Metachromatic blast blast-criteria, metachromatic granules

may be predominant in MCL; also seen in ASM or SSM; prognosis in SM

Atypical mast cell type II = Promastocyte

immature or mature cell, bi- or polylobed nuclei

frequently seen in MCL and ASM; also in SSM; rarely seen in patients with ISM; reduced probability of survival in those with > 5% atypical mast cells type II (of all mast cells)

Atypical mast cells Type I i. cytoplasmic surface-projections (spindle)†

predominant cell type in most patients with ISM; indicates a good prognosis

ii. oval nucleus†, andiii. hypogranulated†

Mature mast cell round cell, round nucleus, well granulated

usually seen together with atypical mast cells type I in patients with ISM; if most cells are round and mature, consider the rare sub-variant ‘well differentiated SM’ (± KIT F522C or other KIT mutations)

*Respective criteria have been published previously [54], †Mast cells have to fulfil two or three of these criteria to be called atypical mast cells type I, the most frequent cell being the spindle-shaped mast cell. AHNMD, associated clonal haematological non mast cell lineage disorder; MDS, myelodysplastic syndrome; AML, acute myeloid leukaemia; ASM, aggressive systemic mastocytosis; SSM, smouldering systemic mastocytosis; ISM, indolent systemic mastocytosis.

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Sampling of cells

The bm aspirate (1–2 mL) should be recovered in EDTAor heparin [59]. Cells should be processed within 24 h. Theymay be kept at 4

°

C up to room temperature in EDTA. Withheparinized samples, storage at 4

°

C is recommended [59].After antibody exposure, erythrocyte lysis is performed withan appropriate lysing-solution [59].

Staining-protocol and selection of markers and fluorochromes

A multiparameter staining-protocol with suitable com-binations of antibodies and fluorochromes should beemployed [57–59]. The minimal standard panel recom-mended includes CD2, CD25, CD45, and CD117 [57–59].Using this panel, MC are defined as CD117

hi

/CD45

+

cellswith typical autofluorescence in the forward/side scatter.When MC display low levels of CD117, it may be preferableto add CD34 and to define MC as CD34

–

/CD117

+

/CD45

+

cells. Staining reactions are reported positive when themean fluorescence intensity (MFI) exceeds the MFI of theisotype-control by 200%. If only subpopulations of MCdisplay CD2 or CD25, the result is still accepted as ‘posi-tive’. In the selection of fluorochromes, it is important toconsider that CD2 is a weak marker in SM [57–59]. There-fore, CD2 should be examined using a sensitive fluoro-chrome such as phycoerythrin [59]. Before being appliedin routine diagnosis, each staining-protocol should undergovalidation. The protocol should be regarded as useful andapplicable when CD117-positive bone marrow MC intypical ISM are demonstrated to co-express CD25 in morethan 80% of all cases.

KIT

-D816V and other

KIT

-mutations

In most adults with SM (> 80%), neoplastic MC exhibita somatic ‘autoactivating’ mutation at codon 816 of

KIT

[60–67]. The D816V mutant is most commonly detected[60–70]. Other

KIT

mutations are rare [62,64,65,68–71].This holds true for somatic mutations as well as germlinemutations found in the rare cases of familial mastocytosis(Table 3) [70–76]. When employing

KIT

mutations as a cri-terion of SM, it is important to be aware that such mutantsare also found in (a few) patients with germ cell tumours andother neoplasms with or without coexisting SM [76–80].

Recommended tissues and cells for KIT-mutation analysis

In suspected SM, the diagnostic standard is to examineunfractionated bone marrow cells (after erythrocyte-lysis)or marrow mononuclear cells (MNC) for

KIT

mutations.The marrow aspirate (1–2 mL) is recovered in EDTA orheparin. If no aspirate sample is available, cells detachedfrom marrow smears or paraffin-embedded biopsy materialcan be employed, if the procedure (mutation-analysis) hassufficient sensitivity [71].

In typical ISM, peripheral blood MNC are often negativefor KIT-D816V, thereby contrasting SSM [81–84]. There-

fore, peripheral blood is not acceptable as an alternativeto bone marrow when searching for

KIT

-mutations insuspected SM. Demonstration of KIT D816V in the skinis indicative for MIS, but is not diagnostic for SM.

Isolation and storage of diagnostic material

Standard-methods for the storage of cells and isolation oftotal RNA or DNA can be applied provided that the yieldof RNA/DNA is sufficient. Isolated RNA or DNA shouldbe evaluated by measuring optical density and purity.Extracted RNA should be stored at

−

70

°

C and DNA at orbelow

−

20

°

C.

Standard-assays for detection of KIT-D816V

Several techniques for detection of KIT D816V have beenreported in the literature [60–64,66–76,83–85]. Based onliterature data and a round robin project performed in thecontext of the consensus-conference, the most sensitive andthus recommended assays are (i) RT-PCR + RFLP (ii)PNA-mediated PCR, and (iii) allele-specific PCR. Thesetechniques should be regarded as standard provided thatthey show sufficient specificity and precision, and are ableto detect KIT-D816V in bone marrow MNC or unfraction-ated marrow cells in > 70% of patients with typical ISM.RT-PCR and RFLP should be performed using publishedprotocols [61–64,67,83–85]. Total RNA is usually employedas starting material. For gel electrophoresis, SYBR-Green-staining is recommended. For PNA-mediated PCR, werecommend the use of a recently published protocol [71].

Table 3 KIT mutants detectable in patients with mastocytosis

KIT mutant

Mastocytosis variant (estimated frequency)

Other non mast cell-lineage disorders

D816V SM (70%−90%), CM (10%−30%)

GIST (< 1%), AML (< 5%), germ cell tumours (10%−20%)

D816Y SM (< 5%), CM (< 5%)

D816F* SM (< 5%), CM (< 5%)

D816H SM (< 5%) germ cell tumours (5%−10%)

R815K* CM (< 1%)I817V SM (< 1%)D820G SM (< 1%)E839K* CM (< 1%)V533D* CM (< 1%)V560G SM (< 1%) GIST (< 5%)V559A* CM (< 1%)F522C† SM (< 1%)del419† SM-familial type (< 1%) GIST-familial typeK509I† CM/SM-familial type (< 1%)A533D*† CM-familial type (< 1%)

*So far only reported in children; †described as germ line mutations; GIST, gastrointestinal stromal cell tumour.


443



,

37

, 435–453

The advantage of this assay is that it exhibits a high sensi-tivity, and that apart from

KIT

-D816V, other mutations incodon 816 are also identified [70,71].

Recommendations for cases with a negative KIT D816V test result

In rare cases with SM, no

KIT

mutation at codon 816 isdetectable. In patients with small-sized MC infiltrates, anegative result must be interpreted with caution, as here

KIT

mutations may only be detected in highly enriched(sorted or micromanipulated) MC [70,83,84]. However,enrichment is not standard and not required in clinicalpractice, as in such patients demonstration of KIT-D816Vhas no therapeutic consequence. However, in patients withaggressive SM (huge MC-infiltrates) studies demonstratingthe absence of

KIT

-D816V are important because wt KITand certain KIT mutants represent targets of imatinib,whereas

KIT

D816V introduces resistance [7,8,13,86].Therefore, a negative result should be confirmed, preferablyin a reference laboratory. This is then followed by examinationof KIT for other mutations in codon 816. If no codon 816mutation is found, sequencing of KIT should be considered.

Serum tryptase

Tryptase remains the recommended serum test to employin the diagnostic work-up for suspected SM [9,10,87–93].Almost all patients with SM have serum total tryptaselevels exceeding 20 ng mL−1, which is a minor SM-criterion[9,10,87–93].

Serum sampling, storage, and assay

The collected blood sample may be stored at 4 °C to roomtemperature for several hours before centrifugation. Result-ing serum samples can be stored for several days at or below4 °C, and maintained at −20 °C (or below) for several years.The test assay currently proposed is a fluoroimmuoenzymeassay which exhibits sufficient sensitivity and detects allvariants of MC tryptases, to yield total tryptase [94].

Normal values and limitations

The median serum tryptase level in healthy adults isapproximately 5 ng mL−1 [87–94]. It may be slightly lowerin children. Tryptase levels are not affected by pregnancy,food-intake, or physical exercise [95]. Severely impairedrenal function is associated with a slight increase in tryptase[96]. In severe allergic reactions, tryptase may becomemarkedly elevated [87,90]. Here, the recommended stand-ard is to wait at least two days following clinical resolutionbefore measuring basal tryptase levels [90]. If tryptaseremains elevated, SM should be considered.

The differential diagnosis of an elevated tryptase alsoincludes myeloid non-MC-lineage neoplasms such as acute(AML) or chronic myeloid leukaemia (CML), myeloprolif-erative disorders (MPD), and MDS [43,92,97]. In these

patients, serum tryptase levels may be elevated in theabsence of a coexisting SM [43,92,97]. Therefore, a tryptaselevel > 20 ng mL−1 counts as minor SM-criterion only inthe absence of an AHNMD [9,10].

Tryptase levels in subtypes of mastocytosis

Tryptase levels tend to be higher in patients with a highMC burden [88,89,92,94,98]. In most patients with CM,tryptase levels are < 20 ng mL−1 [88,89,92]. In typical ISMand SM-AHNMD, tryptase levels range from normal tomarkedly elevated [88,89,92,99]. In ISM, tryptase levelsusually remain reasonably constant over years, whereas inASM or MCL, tryptase levels often increase, especially asthe disease progresses [11,98,100].

Tryptase for monitoring of responses to therapy

In patients with ASM or MCL, tryptase levels usuallydecrease with successful cytoreduction [11,100,101].Tryptase is thus recommended as a surrogate marker forevaluating responses to cytoreductive drugs. However,remission evaluation has to be based also on BME (tryptaseIHC to compare the infiltration grade) by consensus [11].

Apart from tryptase, other MC-related moleculesincluding histamine and its metabolites, soluble KIT, orsoluble CD25, may also serve as surrogate markers ofSM [98,99,102–106]. However, the added value of thesemarkers remains to be determined.

Systemic mediator-related symptoms

Systemic mediator-related symptoms (documented bysubscript-appendix SY, e.g. ISMSY) may be recorded in alldisease-variants and may involve various organ systems.Symptoms may be chronic or acute with an attack lastingminutes to hours [3–8,107,108]. Typical symptoms includehypotension, nausea, headache, and fatigue. The severity ofattacks may range from mild to life-threatening hypotension[107,108].

General approach for assessing and evaluating symptoms

As a first step, unrelated diseases must be excluded asthe basis of symptoms or be identified as co-initiators.Then, an evaluation for potential inciting agents or eventsis started. Although the agents or situations that bring onsymptoms may be ‘IgE-independent’, this search doesinclude the determination of total and of specific IgE. Skinprick testing should be performed with caution.

Grading of symptoms

The following grading system for recording of symptomsis proposed: grade 0 (no symptoms), 1 (mild, no therapyrequired), 2 (moderate, kept under control with antimediator-type drugs), 3 (not sufficiently controlled with therapy), andgrade 4 (SAE) (Table 4a). The frequency of grade 4 events

444 P. Valent et al.

© 2007 The Authors. Journal Compilation © 2007 Blackwell Publishing Ltd, European Journal of Clinical Investigation, 37, 435–453

is also recorded: A (< 1/year), B (> 1/year and < 1/month),and C (> 1/month). Severe hypotension and cardiovascularcollapse resembling anaphylaxis may occur in any diseasecategory. Whereas in true anaphylaxis, an allergen is com-monly identified [109–111], this is usually not the case inmastocytosis (allergies are no more frequent in patients withmastocytosis than in the general population). Nevertheless,some patients may suffer from overt (coexisting) allergy. Theclassification of ‘anaphylaxis’ in mastocytosis is thus related tothe presence (+) or absence (–) of IgE-specific incitating agents.

Therapy of systemic mediator-related symptoms

It is standard to instruct all patients to avoid agents and situ-ations that precipitate a reaction. Patients at risk for severehypotension are advised to carry 2 or more epinephrine-self-injectors and are taught to use them under prescribedconditions. In general, antimediator-type drugs are appliedin a step-wise fashion and on the basis of the organ(s)affected (Table 4b) [3,4,6,107,108]. In patients with IgE-dependent anaphylaxis, specific immunotherapy should be

Table 4a Grading of constitutional and mediator-related symptoms in patients with mastocytosis*

Grade Definition

0 = no symptoms prophylaxis†, no specific therapy required

1 = mild, infrequent prophylaxis ± as needed therapy2 = moderate requires therapy, can usually be kept

under control3 = severe suboptimal or unsatisfactory control

with daily and combination therapy4 = severe adverse event‡ requires emergency therapy and

hospitalization

*Most frequent symptoms to be graded: headache, nausea, systemic hypotension/anaphylaxis, †all patients with mastocytosis are advised to avoid precipitating factors and for most of them, prophylactic antihistamines (H1 and H2 histamine receptor antagonists) are recommended, ‡the frequency of severe adverse events should be reported: A: < 1/year; B: > 1/year and < 1/month; C: > 1/month.

Table 4c Systemic mediator-related symptoms in mastocytosis: proposed response criteria*

Response Definition

Complete regression (CR)

all symptoms completely resolved and not observed again during 12 months after therapy

Continuous CR (CCR) no further symptoms after 2 years†

Major regression (MR) improvement of symptoms by > 50% or/and decrease in frequency of severe (grade 4) events from B to A or from C to B

Partial regression (PR) improvement to 10–50% or/and minor decrease in frequency of severe events (less than defined for the MR group – see above)

No regression (NR) < 10% improvement and no decrease in frequency of severe events

*The best result counts regardless of the duration of regression – exception: in patients with grade 4B or 4C disease, CR or MR can only be recorded when the frequency of severe attacks did not increase over time, which requires a careful follow up of the patient. †In patients with CR, the remission status is carefully examined over time. If no further attacks are recorded after 2 years of observation, CR becomes CCR = continuous complete regression.

Table 4b Stepwise application of mediator–targeting drugs in CMSY/SMSY

Clinical symptoms and mediator effects Step* Drugs to be considered†

Cardiovascular Recurrent hypotension and tachycardia

1 H1 + H2 histamine receptor antagonists

2 Glucocorticoids3 Aspirin in select cases (if tolerated)

Recurrent shock (in symptom-poor interval)


2 H1 + H2 histamine receptor antagonists and low dose oral glucocorticoids

3 Experimental antimediator-type drugs

With a coexisting allergy (specific IgE demonstrable)


2 Specific immunotherapy (if trigger known)

3 Additional short-term oral glucocorticoids

Gastrointestinal tract Peptic ulcer disease + bleeding (ASM/MCL)

1 H2 histamine receptor antagonists2 Proton pump inhibitors + H2

blockers3 fibrinogen, coagulation factors,

protamine, or platelets on demand

Diarrhoea, abdominal pain,Abdominal cramping,Nausea, vomiting


2 Oral cromolyn sodium3 Consider leukotriene antagonists4 Short-term glucocorticoids

Skeletal system Pain without osteopenia/osteoporosis

1 Analgesics, NSAIDs (if tolerated), and opiates in severe cases

2 Consider radiation in severe cases

Severe Osteopenia or osteoporosis

1 Oral bisphosphonates2 Intravenous bisphosphonates3 Interferon-alpha

Neurological Symptoms Headache, others


2 Oral cromolyn sodium

*in all cases, the first manoeuvre is to avoid triggering factors, †All patients at risk are advised to carry epinephrine self-injectors and to use them under prescribed conditions;

NSAIDs, non-steroidal anti-inflammatory drugs.

Consensus on Standards in Mastocytosis 445


considered with recognition of potential risks [112–114]. Inthe absence of specific IgE, however, immunotherapy is notrecommended. Also, cytoreductive agents are not recom-mended for treatment of mediator-related events.

Evaluation of responses to therapy

Responses to therapy are recommended to be classified asCR (complete resolution), MR (> 50% reduction in severityor/and significant decrease in frequency: B→A or C→B),PR (10–50% reduction in severity; no major decrease infrequency), and NR (< 10% reduction; no decrease infrequency) (Table 4c). Continuous CR (CCR) is definedas symptom-free interval of at least two years following theinitiation of therapy.

Associated clonal haematological non MC-lineage disease (AHNMD)

An AHNMD is diagnosed in up to 30% of all cases withSM [1–3,5–11,70,115–121]. Both the SM-componentand AHNMD-component of the disease should be clas-sified according to WHO criteria (Fig. 1a) [9,10,122–127].Most patients have a myeloid neoplasm [70,115–122].Less frequently, a lymphoid (usually B-cell) neoplasm suchas a plasma cell myeloma, is diagnosed [70,115–121].

Myeloid leukaemias, MPD, MDS, and MPD/MDS

Ph+ CML is rarely diagnosed in SM [121]. More frequentdiagnoses are SM-CMML and SM-AML (Table 5a)[9,10,70,115–121]. The most frequent chromosomal defectin SM-AML is t (8;21) (Table 5a) [50–53,128,129]. In SM-AML with small-sized MC infiltrates, the SM-componentmay be overlooked (occult SM) [52,53]. The clinical courseof SM-AML is similar to that observed in AML withoutSM. Responses to chemotherapy may also be comparable,although patients without SM may have a better survival[53,128,129]. Nevertheless, the standard recommendationis to treat patients with myeloid leukaemias plus SM asif SM was not present. The reverse is also true, i.e. to treatthe SM-component of the disease as if no leukaemia existed[9,10].

Various types of MPD and MDS have been reportedto occur in patients with SM [9,10,70,119,120]. The most

Table 5a AHNMD detected in SM-AHNMD*

Disease variant

Cytogenetic or molecular marker Comments

SM-CML KIT-D816V usually no Ph-chromosomeand BCR/ABL found; oftenreported as atypical CML

SM-CMML KIT-D816V KIT-D816V often found inmast cells and monocytes, patients often progress tosecondary AML

SM-AML-t(8; 21)

t(8; 21) – AML1/ETO and KIT-D816V

other translocations and gene defects occur, but arerarely seen in SM-AML.SM often presents as ‘occultmastocytosis’ in SM-AML (at first presentation)

SM-CEL CHIC2 deletions† – FIP1L1/PDGFRA

in most cases of SM-CEL, KIT-D816V is not detectable

*The SM component of the disease should be determined in all cases.

In patients with SM-CMML, the SM component often is ASM (ASM-CMML); whereas in those with SM-AML, the SM component usually is ISM (ISM-AML).

†In all cases of SM-eo, bone marrow cells should be screened for the presence of a CHIC2 deletion by FISH. AHNMD, associated clonal haematological non mast cell lineage disorder; SM, systemic mastocytosis; CML, chronic myeloid leukaemia; AML, acute myeloid leukaemia; CEL, chronic eosinophilic leukaemia.

Table 5b Special studies recommended in patients with SM-eo*

Key signs/markers of the disease Technique

Disease (differential diagnosis)

CHIC2 delFIP1L1/PDGFRA

FISH RT-PCR

SM-CEL SM-CEL

Signs of endo- myocardial fibrosis Signs of lung fibrosis

Echocardiogram Electrocardiogram pulmonary function tests and X-ray

SM-HES, SM-CELSM-HES, SM-CEL

t(9; 22), Ph + & BCR/ABL

Cytogenetic, FISH RT-PCR, SB

SM-CML (Ph + CML) (basophilia/eosinophilia)

inv16 CBFβ/NYH11

Cytogenetics, FISH, and RT-PCR

SM-AML-inv16 (WHO) = SM-AML-M4eo (FAB)

T cell receptorRearrangement

PCR SM-NHL-T with associated eosinophilia

Lymphadenopathy,Lymphomas

sonography/CT of lymph nodes and X-ray of chest

SM-NHL, ASM with eosinophilia†

Hepatomegaly,Splenomegaly

sonography/CT of the abdomen

SM-NHL, ASM with eosinophilia†

Questionable – reactive vs. MPD or SSM

CFU-GM signs of inflammation or parasites

if elevated: suspect MPD reactive eosinophilia? parasitic disease?

*The checkpoint SM-eo is defined by SM criteria and a constant elevation of peripheral blood eosinophils above 1500 µL−1.

†ASM is frequently associated with marked eosinophilia – a special sub-variant is lymphadenopathic mastocytosis with eosinophilia.

FISH, fluorescence in situ hybridization; SB, Southern blot; SM, systemic mastocytosis; CEL, chronic eosinophilic leukaemia; CT, computed tomography; AML, acute myeloid leukaemia; NHL, non-Hodkin lymphoma.



frequent overlap-disease in SM is CMML. The treatmentplan for the MPD/MDS should be prepared as if no SMwas diagnosed.

‘SM with eosinophilia’ (SM-eo)

An important decision-point in the AHNMD-algorithm is‘SM with eosinophilia (SM-eo) defined by a persistentincrease in circulating eosinophils to > 1500 µL−1 [3,12,13,82,131]. In these patients, several diagnoses have to beconsidered, and respective criteria and markers applied(Table 5b). In those with the FIP1L1/PDGFRA fusion-geneand/or a CHIC2-deletion, the diagnosis is SM with ‘chroniceosinophilic leukaemia’ (SM-CEL) following WHO criteria(Table 5b). In patients with CEL-related organopathy, butno marker of monoclonal eosinophils, the final diagnosis isSM with ‘hypereosinophilic syndrome’ (SM-HES).

However, not all patients with SM-eo have HES or CEL:rather, many have ASM, SM-AHNMD, or even ISM. Anotherimportant aspect is that organ damage caused by ASM (C-Findings) can clearly be distinguished from CEL-relatedorgan-damage (cardiopathy, lung-fibrosis). Likewise, SM-related eosinophilia is not associated with lung fibrosis orcardiopathy even after a course of (many) years [82]. Thus,SM-eo is a pre-diagnostic checkpoint, but is not a finaldiagnosis or subcategory of SM. Treatment of patientswith SM-eo depends on the final diagnosis. In those withSM-CEL and FIP1L1/PDGFRA, treatment with imatinibis recommended using the same dose and schedules as inCEL without SM.

B- and C-findings and recommendations for selection of patients for intensive and targeted therapy

A major challenge in mastocytosis is appropriate selectionof patients for intensive or targeted therapy. The selectionprocess should be based on signs and symptoms of aggressivedisease = C-Findings [9–11] (Table 6a). Thus, C-Findingsare the result of a clinically relevant impairment or loss oforgan function caused by local MC-infiltrates (Fig. 1b) [9–11].When designing clinical trials with cytoreductive or targeteddrugs, C-Findings should be included as primary inclusioncriteria for patient selection. The presence of an aggressiveMC-infiltrate should be documented by biopsy when safetyis appropriate [11].

In contrast to C-Findings, B-Findings are not indicativeof aggressive disease and should not lead to the decision totreat unless B-Findings progress (convert to C-Findings)[11]. The standard-message is: B: Borderline Benign –Be careful and wait and watch if progression occurs; C:Consider Cytoreduction with Chemotherapy or withTargeted Drugs.

B-Findings include signs of multilineage-involvement(hypercellular marrow, dysplasia), a massive MC burden (hugeMC marrow infiltration, serum tryptase > 200 ng mL−1),and organomegaly (spleen, liver, lymph nodes) [9,10,56].If B-Findings (=2) are documented, the diagnosis is SSM(Fig. 1a) [9,10,56]. The prognosis and natural course in

SSM is variable. Many patients remain in a smoulderingstate for decades [56,82].

Response criteria for patients receiving cytoreductivedrugs have been generally agreed upon and should beapplied in all patients [11]. These criteria strictly relate toC-Findings, and thus are only applicable to patients withASM or MCL. Based on these criteria, a complete response,a partial response, a minor response, and no response, haveto be distinguished (Table 6b) [11].

The gastrointestinal (GI) tract

Endoscopy (with histology) should be performed in patientswho have GI symptoms, C-Findings, or a history of GI tractdisease. Since the GI tract contains significant numbers ofMC under physiological conditions, only the multifocalcompact MC-infiltrate (> 15 MC/aggregate) counts asmajor SM criterion. However, the absence of MC infiltratesdoes not exclude mediator-related symptoms or ulcerativedisease in the context of a known SM [132–134]. If mal-absorption or weight loss occurs, aggressive SM must beconsidered.

GI symptoms to be graded include diarrhoea, abdominalcramping, ulcerative disease, and GI tract bleeding. Thesesymptoms are graded as in Table 4a.

Treatment of mediator-related symptoms starts withhistamine-receptor antagonists (Table 4b). Proton pump-inhibitors or oral sodium cromoglycate are considered asnecessary (Table 4b). GI bleeding requires additional ther-apy adapted to the specific clinical situation (note: in thosewith coagulopathy or/and thrombocytopenia, ASM andMCL must be considered). Response criteria for GI tractsymptoms are the same as those applied for other mediator-related symptoms (Table 4c). In case of C-Findings, themost important therapy is cytoreduction. Respective responsesare classified as in Table 6b [11].

Skeletal involvement

Skeletal pathology in SM includes osteosclerosis, osteopenia,osteoporosis, and osteolysis [11,31–33]. Whereas osteolysisis usually seen in advanced disease [13], osteoporosismay develop in any SM-variant [11,31–33]. The leadingsymptom is musculoskeletal pain which can be severe andresistant to conventional analgesia. The most relevant con-sequence of osteopathy is bone-fracture, the most commonsite being the spine.

Bone mineral density (BMD) measurement using dualX-ray absorptiometry (DXA) should be performed in allSM patients. Sites commonly measured include the lumbarspine and hip. The diagnosis is established according toWHO-criteria defining osteopenia (T score < −1 and > −2·5)and osteoporosis (T score < −2·5). An X-ray of bonesshould be performed to exclude local osteopathy (osteolysis,fractures). Osteolyses are described as solitary or multiplewith the diameter noted. In doubt about their aetiology, abiopsy with tryptase-IHC should be performed (if possible).



Mild osteopenia does not necessarily require therapyunless risk factors are noted (e.g. glucocorticoid-therapy).If the T score is < −1, pharmacological intervention shouldbe considered. If the T score is < −2, therapy must bestarted. For osteoporosis in SM, oral bisphosphonatesare recommended. In severe cases or patients with drug-intolerance, intravenous bisphosphonates (schedulesand safety-measures as in multiple myeloma) or low-doseinterferon-alpha are applied (Table 4b). Patients withosteolysis and pathological fractures are candidates forcytoreductive drugs (plus bisphosphonates). Local irra-diation should be considered where resistant bone painis present.

Response to treatment of osteoporosis is monitored byyearly BMD-measurements using DXA. Loss of height oracute back pain warrants repeated spinal X-rays to docu-ment or exclude new vertebral fractures. Responses of painand osteoporosis (DXA) should be evaluated as in Table 4c,and changes in osteolytic lesions, considered a C-Finding,by criteria shown in Table 6b [11].

Neurological and non-organic symptoms and QOL

Neurological and psychiatric symptoms in mastocytosis rangefrom mild to severe. Sometimes, it may be difficult to separate

Table 6a Selection of patient with systemic mastocytosis (SM) for cytoreductive or targeted drugs and treatment plan

Table 6b ASM and MCL: response criteria by B/C-Findings

Step A: Ask for C-Findings andestablish the diagnosis ASM, MCL, or mast cell sarcoma;if no C-Findings can be documented and there areno criteria for ASM, MCL, or mast cell sarcoma, the patient is usually not a candidate for cytoreduction, chemotherapy, or targeted drugs

Step B: Ask for targets of drug therapy: wt KIT, KIT-D816V, others; and exclude an AHNMD as the primary cause of C-Findings !Step C: Define the treatment plan for ASM/MCL-patients:

KIT-D816V: a) interferon-alpha plus glucocorticoidsb) in interferon-intolerant patients or those in whom no response is seen → 2CdA (cladribine)c)* in highly aggressive cases or those who relapse or have MCL at diagnosis → consider

polychemotherapy – if there is a clear response to (chemo)therapy →d) consider stem cell transplantation

other targets: a) select suitable targeted drug†b) if there is no response – proceed as in patients with KIT-D816V

*These patients are also candidates for novel investigational (targeted) drugs such as dasatinib or PKC412, preferably in clinical trials. If there is a clear response to such investigational drug, the patient should be considered for stem cell transplantation – i.e. the protocol should allow for such switch to conventional (potentially) curative therapy, †Patients with wt KIT or noncodon-816 mutations in KIT may show a response to imatinib or other tyrosine kinase inhibitors.

I: Major response:Complete resolution of at least one = one or moreC-Finding(s) and no progression in other C-Findings(a) Complete remission = with disappearance of mast cell infiltrates in affected organs and decrease of serum tryptase levels to

< 20 ng mL−1 and disappearance of SM-associated organomegaly(b) Incomplete remission = with decrease in mast cell infiltrates in affected organs and/or substantial decrease of serum tryptase level

and/or visible regression of organomegaly(c) Pure clinical response = without decrease in mast cell infiltrates, without decrease in tryptase levels, and without regression of

organomegaly

II: Partial response:Incomplete regression of one or more C-Finding(s)*without complete regression and without progress(a) Good partial response: > 50% regression†(b) Minor response: < 50% regression†

III: No response:C-Finding(s) persistent or progressive(a) Stable disease: C-Finding-parameters show constant range(b) Progressive disease: one or more C-Finding(s) show progression

*With or without decrease in mast cell infiltrates, serum tryptase levels, and organomegaly.†No progression in other C-Findings are documented.



Table 7a Master score for grading and evaluation of patients with mastocytosis

Finding/symptom Yes/no Define and specify

Category of disease CM/SM: ________ WHO category: ________Serum tryptase ng/mL: ________B-Finding(s) ________ number of B-Findings (n): ________

organ: ________ finding: ________organ: ________ finding: ________

C-Finding(s) ________ organ: ________ finding: ________organ: ________ finding: ________

AHNMD ________ subtype by WHO criteria:________Skin lesions ________ Subtype (CM): ________ Extent (%) ________Skin symptoms:Flushing ________ Grade (0–4): ________ 4-A/B/C: ________Pruritus ________ Grade (0–4): ________ 4-A/B/C: ________Blistering/bullae ________ Grade (0–4): ________ 4-A/B/C: ________

Systemic mediator-effects (SY) ________ Grade (0–4): ________ 3/4-A/B/C: ________identified trigger(s): ________

Constitutional or cardiovascular describe symptoms: ________Hypotension (+/–): ________ – A/B/C: ________Specific IgE (+/–): ________

Skeletal involvement (mediator-related):Osteopenia* ________ T-score (–1 to −2·5): ________Osteoporosis* ________ T-score (<−2·5): ________Osteolysis* ________ location, size and number: ________Pain* ________ Grade (0–4): ________ 4-A/B/C: ________

GI-tract involvement (mediator-related)Cramping* ________ Grade (0–4): ________ 4-A/B/C: ________Diarrhoea* ________ Grade (0–4): ________ 4-A/B/C: ________Ulcus duodeni* ________ Grade (0–4): ________ 4-A/B/C: ________Ulcus ventriculi* ________ Grade (0–4): ________ 4-A/B/C: ________

Neurological symptoms ________ Degree (a/b†): ________ Symptoms/findings: ________Psychological ________ Degree (a/b†): ________ Symptoms/findings: ________Psychiatric ________ Degree (a/b†): ________ Symptoms/findings: ________

ECOG + QOL ECOG (0–4): ________ QOL: ________

*Possibly related to mastocytosis; †a, no therapy required; b, therapy required.

Table 7b Overall response score-form for patients with mastocytosis*

VariableBefore therapy

After therapy Finding/symptom Describe

Define best response*

CCR (yes/no)†

Category of disease (WHO) ________ ________ C-Findings ________ ________ ________Serum Tryptase (ng/mL) ________ ________ Overall haematological ________ ________ ________B-Findings ............. (n =) ________( ) ________( ) response (B + C)C-Finding ............. ________ ________ AHNMD ________ ________ ________QOL ________ ________ Skin lesions ________ ________ ________ECOG ________ ________ Skin symptoms ________ ________ ________Osteopathy (T score) ________ ________ Constitutional ________ ________ ________Neurological symptoms (a, b) ________ ________ Cardiovascular ________ ________ ________Psychological symptoms (a, b) ________ ________ Hypotension‡ ________ ________ ________Psychiatric symptoms (a, b) ________ ________ Osteoporosis ________ ________ ________

Bone pain ________ ________ ________Cramping ________ ________ ________Diarrhoea ________ ________ ________GI tract ulcus ________ ________ ________

*For exact evaluation of responses in symptoms and B/C-Findings, see Tables 1c, 4c, and 6b.†CCR is evaluated (at least) 2 years after the start of therapy.‡Includes anaphylaxis.



these symptoms from mediator-related symptoms. Moreover,it is usually difficult, if not impossible, to link non-organicsymptoms to mastocytosis. Currently, there are no guidelinesfor the grading and scoring of neurological or psychiatricsymptoms in mastocytosis. As a general standard, we pro-pose that symptoms are scored and managed by specialistsas if no MC-disease was diagnosed. This should be donewith recognition of the overall situation and after havingworked out a general treatment plan in a multidisciplinaryapproach. In addition, we recommend classifying patientsaccording to treatment dependence of symptoms, i.e.group ‘a’ (no specific ‘neurological’ or ‘psychiatric’ therapyrequired) and ‘b’ (specific therapy required). For QOL,the recommendation is to use generally accepted question-naires, adapted for mastocytosis, in practice and clinicaltrials.

Global grading

The complexity of mastocytosis requires investigation ofmultiple symptoms, signs, and laboratory findings. To assistin evaluation, we provide a master score form (Table 7a)which represents a synthesis of staging and grading resultsand should facilitate the management of patients, especiallyin the follow-up (one form per visit). For evaluation of treat-ment responses, we also recommend using score forms, anexample being depicted in Table 7b.

Acknowledgements

All persons listed as co-authors contributed to the pre-conference discussion and post-conference discussion phaseof the meeting (May 2005 until April 2006) and activelyparticipated in the Standardization Conference in Vienna(November 3–6, 2005). All co-authors contributed equallyby discussing criteria, standards, algorithms, and recommen-dations at the Working Conference. In addition, all personslisted as co-authors provided essential input by draftingparts of the manuscript and by approving the final versionof the document.

We wish to thank the following experts for helpful dis-cussion in the pre-conference phase, support in preparationof the conference, and input in manuscript preparation:Magdalena Lange, Ayalew Tefferi, Friedrich Wimazal,Jürgen Grabbe, Rosa Nunez, Alain Moussy, BoguslawNedoszytko, and Torsten Zuberbier.

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