Gastrointestinal tract spindle cell lesions -
histological and molecular features
Luigi Terracciano
Staffmeeting 23.1.2019
GIST
Epidemiology
• 1 case / 100.000 / year (GISTs clinical significant, >2 cm)
• Micro GISTs (< 1cm) are quite common. Autopsy studies up to
22.5% (Agaimy A, Am J Surg Pathol, 2007)
• From children to elderly (64ys median age)
• Equal sex distribution (in children >> female)
• > Sporadic; rarely in tumor syndromes
• Stomach (60%), jejunum and ileum (30%), duodenum (5%), colon
&rectum (< 5%). Rarely in esophagus, appendix and gallbladder
• E-GISTs: omentum, mesentery, retroperitoneum and perineum
Macroscopic Findings
• From 1 mm to > 20 cm
• Median size: stomach 6 cm, duodenum
4.5 cm, jejunum / ileum 7 cm
• Well-circumscribed solitary lesion,
centered on the wall of the gut
• Rarely, multiple lesions in the stomach
(> pediatric and micro GISTs) or in the
small bowel (> familial GISTs and GISTs
associated with neurofibromatosis)
• Frequently ulcerate the overlying
mucosa
• Tan and fleshy with frequent cystic
changes and hemorrhage
Microscopic Findings
Spindle cell (70%) Epithelioid (20%)
Minimal cytologic atypia Neuroendocrine or „paraganglioma“
like-features
Immunohistochemical Findings
• KIT (CD117): nearly 95% of cases (cytoplasmic, membranous, dot-like
perinuclear). Highly sensitive but relatively low specific (> melanomas!)
5% negative (> PDGFRa mutant GISTs)
• DOG1: (discovered on GIST1, ANO1): very sensitive and more specific,
positive also in KIT –ve GISTs
• CD34: 70% of cases
• H-caldesmon : 60-70%
• Smooth muscle actin: 30-40%
• S-100: 5%
• Desmin, cytokeratin: 2%
CD117 DOG1
SMA S100
TUMOR PARAMETERS RISK OF PROGRESSIVE DISEASE* (%), BASED ON SITE OF ORIGIN
Mitotic Rate
Size Gastric Duodenum Jejunum/Ileum (and EGISTs)
Rectum
≤5 per 50 HPF (5 mm2)
≤2 cm None (0%) None (0%) None (0%) None (0%)
>2, ≤5 cm Very low (1.9%) Low (8.3%) Low (4.3%) Low (8.5%)
>5, ≤10 cm Low (3.6%) (Insuff. data) Moderate (24%) (Insuff. data)
>10 cm Moderate (10%) High (34%) High (52%) High (57%)
>5 per 50 HPF (5 mm2)
≤2 cm None** (Insuff. data) High** High (54%)
>2, ≤5 cm Moderate (16%) High (50%) High (73%) High (52%)
>5, ≤10 cm High (55%) (Insuff. data) High (85%) (Insuff. data)
>10 cm High (86%) High (86%) High (90%) High (71%)
Histological risk factors for conventional GISTs AFIP and College of American Pathologists
Miettinen M, Lasota J, Semin Diagn Pathol, 2006
RISK CATEGORY TUMOR SIZE (cm) MITOTIC INDEX (PER 50 HPFs)
PRIMARY TUMOR SITE
Very low risk
<2.0 ≤5 Any
Low risk 2.1-5.0 ≤5 Any
Intermediate risk 2.1-5.0 >5 Gastric
<5.0 6-10 Any
5.1-10.0 ≤5 Gastric High risk Any Any Tumor rupture
>10.0 Any Any
Any >10 Any
>5.0 >5 Any
2.1-5.0 >5 Nongastric
5.1-10.0 ≤5 Nongastric
Histological risk factors for conventional GISTs
II Joensuu Criteria
Joensuu H, Hum Pathol, 2008
Joensuu H, Lancet Oncol, 2012
Additional morphological criteria: coagulative necrosis, mucosal invasion,
ulceration, proximal location in stomach versus antrum.
Frequency of the molecular GIST subtypes
Schematic representation of KIT and PDGFRA with main
mutational hotspots
Cioffi A & Moki RG, J Clin Oncol, 2015
KIT Exon 11:
• Interstitial deletions between
codons 550-579 (> 557 and
579 codons)
• Point mutations (> 557, 559,
560 and 576 codons)
• Tandem duplications between
571 and 591 (> gastric GISTs )
Exon 9:
• Duplication of codons 502-503
(small intestine GISTs and >
malignancy)
Exons 13 and 17:
• Point mutations
PDGFRA
• > gastric locations and
epithelioid morphology
• D842V mutation is the most
frequent (56-75%)
Chr 4q12
ATP-binding region
Activation loop
RTK Mutations Localisation
KIT Exon 9 > Small bowel, PDGFRA >> Stomach
Histology
PDGFRA and WT : epithelioid
Prognosis
– KIT exon 9: better relapse free survival after curative resection
– However less benefit from imatinib in adjuvant and metastatic settings : Higher dosis ? Data conflicting !
– Clinical benefit of second line sunitinib
– KIT exon 11 deletions higher risk of relapse (> 557 and 558 del.). → Reclassification of
gastric GISTs of intermediate prognosis as high risk with respect to relapse (Martin-Broto J,
Ann Oncol, 2010, Corless CL, J Clin Oncol, 2014).
– In the metastatic setting confer an exquisity sensitivity to imatinib (Heinrich MC, J Clin Oncol,
2003)
– PDGFRA often indolent (> Exon 18, D842V), > resistance to imatinib, sunitinib and nilotinib. Crenolanib ?
„Wild type“ GIST
• 10-15% without any mutation of KIT and PDGFRA
genes. Too broad and non-specific.
• Young patients
• Lymph node metastasis is frequent
• TKIs are not effective
• Risk stratification should not be used in SDH-deficient
GISTs
„Wild type“ GIST
Succinate Dehydrogenase Deficient GIST
• 42% of wild-type GISTs, 3% of all GISTs, 7,5% of stomach GISTs
• > Gastric location, epithelioid or mixed morphology, multinodular / infiltrative
growth pattern, multifocal, strongly KIT +, loss of SDHB immunohistochemical
expression (27% also lack of SDHA)
• Propensity of lymph node and liver metastasis (50%), but indolent behaviour
• Carney triad: loss of SDHB may be due to hypermethylation of the promoter
region of the SDHB gene
• Carney-Stratakis syndrome: germline
mutations of SDH subunits A, B, C and D
McWhinney SR, N Engl J Med, 2007
Histology of SHD deficient GISTs
SDHB SDHA
SDHB SDHA
DOG1
DOG1
Posttreatment changes
• Most GISTs show some histopathologic response to imatinib, but this is usually incomplete
and does not correlate with clinical or radiologic response
• Necrosis and / or hyalinization; cystic changes, haemorrhage, hypocellularity and
myxohyaline stroma
• Possible loss of CD117 and CD34 positivity ; DOG1 better retained
• Cytological phenotypic changes and possible acquisition of myoid phenotype
Pauwels P, Histopathology, 2005
Liegl B, Am J Surg Pathol, 2009
Rare Mesenchymal Tumors of Gastrointestinal
Tract
• Malignant Gastrointestinal Neuroectodermal Tumor (GNET)
• Synovial Sarcoma
• Kaposi Sarcoma
• Perivascular Epitheliod Cell Tumor
• Leiomyosarcoma
• Malignant peripheral nerve sheat tumor (MPNST)
• Inflammatory myyofibroblastic tumor
• Plexiform fibromyxoma
Gastrointestinal tract spindle cell lesions
Just like real estate, it‘s all about location!
Mucosa to serosa
• Differential Diagnosis: noting whether a tumor is centered in the mucosa,
submucosa, muscularis propria or serosa
• Each type of lesions is often restricted to one of these layers
Voltaggio L, Mod Pathol, 2015
Location of mesenchymal lesions in the GI tract by layer I
Lesion Favored site in the GI tract
Malignant potential
Mucosa Submucosa Muscularis propria
Mesentery
Benign epithelioid nerve sheath tumors
Colon Benign X
Sporadic ganglioneuroma
Colon Benign X
Psammomatous melanotic schwannoma
Esophagus, colon, stomach
Likely benign X
Begnin fibroblastic polyp/perineuroma
Colon Benign X
Leiomyoma Colon Benign
X(associated with muscolaris mucosae)
Kaposi sarcoma Stomach Quasi-neoplastic-related to immune suppression
X
Inflammatory fibroid polyp
Stomach (antrum)
Benign X
Synovial sarcoma
Stomach Malignant X X X
Gangliocytic paragaglioma
Duodenum Low grade-lymph nodes metastases reported
X X
Glomus tumor Stomach Usually benign X
Plexiform fibromyxoma
Stomach Benign X
Location of mesenchymal lesions in the GI tract by layer II
Lesion Favored site in the GI tract
Malignant potential
Mucosa Submucosa Muscularis propria
Mesentery
GIST Stomach Variable X
Gastrointestinal schwannoma
Stomach Benign X
Leiomyoma Esophagus Benign X
Malignant GNET Colon Malignant X
Leiomyosarcoma Colon Malignant
X
Ganglioneuroma- tosis
Colon Benign X X X X
Mesenteric fibromatosis
Small intestine
Benign, local aggressive
X X
Inflammatory myofibroblastic tumor
Small intestine
Variable X X
Sclerosing mesenteritis
Small intestine
Benign X
IgG4-related fibrosclerosing diasease
Small intestine
Benign X
Heterotopic myosistis ossificans
Small intestine
Benign X
Malignant Gastrointestinal Neuroectodermal
Tumor (GNET)
• Also known as gastrointestinal clear cell sarcoma-like tumor
• Around 50 reported cases, increasingly recognized
• Young to middle–aged adults
• Mean age 40 years
• Small bowel (70%), stomach, colon,
• Large infiltrative masses
• Aggressive sarcoma lymph node and liver metastases
Stockman DL, Am J Surg Pathol, 2012
Malignant Gastrointestinal Neuroectodermal
Tumor (GNET)
• Different from conventional clear cell
sarcoma of tendons and
aponeuroses
• Sheet-like, alveolar, pseudopapillary
• Rounded/epithelioid >>spindle cells
• Eosinophilic to clear cytoplasm
• Small nucleoli uniform cytology
• Some tumors with prominent
osteoclast-like giant cells
GNET Histology
Stockman DL, Am J Surg Pathol, 2012
Malignant Gastrointestinal Neuroectodermal
Tumor (GNET): Immunophenotype and Genetics
• Diffuse strong reactivity for S-100 and SOX10
• Lacks melanocytic markers (HMB45, melan-A, MiTF)
• t (12;22) with ATF1-EWSR1
t (2;22) with CREB1-EWSR1
• Diagnosis can be confirmed by FISH
• Aggressive behavior with frequent
lymph nodes and liver metastases
EWSR1
ATF1
Gastrointestinal smooth muscle tumors
Leiomyoma: all segments of GI tract
- mural (> esophagus, 5 times > GIST, but 1:50 in
stomach and small intestine)
- muscularis mucosae (> colon and rectum)
- younger patients than GIST
- > sporadic; Alport syndrome, MEN type1
Cytoplasmic globoid inclusions, desmin + Cave: some GI leiomyomas can be
colonized by KIT+ Cajal cells
Leiomyosarcoma
• Very rare tumor (around 1:50 of GIST)
• After 2000, around 70 reported cases
• Wide age range (18-94 years, median 60 years)
• Small bowel (1 for 30 GISTs), colon, anorectum, stomach and
esophagus (extremely rare)
• Large, bulky tumors (average site > 10 cm); > polypoid growth in
rectum
• Ulceration of the overlying mucosa is common
• Frequent liver and lung metastases; tumor size (≥ 5 cm) indicator
of poor prognosis; smaller tumors have a relatively better
prognosis than GISTs with similar mitotic rates
Yamamoto H, Histopathology, 2013
Morphology
• Histology: spindle
cells, eosinophlic
fibrillary cytoplasm,
cigar-shaped nuclei with
blunt end
• High mitotic rate (>20 /
50 HPF)
•SMA, desmin and
caldesmon +ve ;CD117
and DOG-1 -ve
Epstein-Barr Virus-associated Smooth
Muscle Tumors
Miettinen M, Modern Pathol, 2014
• A rare subset of smooth-muscle tumors in immunosuppressed patients (> AIDS,
solid organ transplant patients)
• Tumor multiplicity is common
• Behavior indolent and unpredictable: mitotic rate not a reliable marker of
malignancy
Synovial Sarcoma
Romeo S, Clin Sarcoma Res, 2015
• Male:female = 3:1
• Age range 17-61 (median 44 ys)
• Stomach, esophagus, small intestine, colon. Size: 2-15 cm (median 8 cm)
• Stomach : mainly monophasic SS, intramural,
Esophagus: Biphasic SS, endophytic
Immunohistochemistry: cytokeratins, EMA and vimentin. CD99, bcl2,TLE1 S-100.
Cave : focal positivity for DOG 1
• FISH: t (X;18) (p11;q11) SS18 (SYT) gene, SSX1, SSX2, SSX4 genes
• Variable prognosis (grading, size)
Synovial Sarcoma
Romeo S, Clin Sarcoma Res, 2015
Thank you for your attention!
Therapy and resistence
• Median overall survival in patients with metastatic GIST:
Before TKIs administration: 20 months (De Matteo RP, Ann Surg, 2000)
After TKIs adminstration: > 5 years (Blanke CD, J Clin Oncol, 2008)
• Roughly 60% of GISTs never experience a relapse and are considered cured
only by surgery
• Localized disease:
• High-risk GISTs: adjuvant therapy of 400mg /day imatinib mesylate over 3 ys
• ( De Matteo RP, Lancet, 2009)
• As a minimum requirements, genotyping should be performed in intermediate-
and high –risk patients as well as in case of neoadjuvant therapy
• Advanced disease:
• Sunitinib malate ( > exon 9 mutations and KIT/PFGRA WT genotype), dasatinib
• Regorafenib
Wada R, Pathol Int, 2016
Gounder M, Cancer Chemother Pharmacol, 2011
Molecular aspects for primary and secondary TKI
resistance in GIST (I)
Primary and secondary resistance to imatinib results in a conformational shift
in the kinase domain of KIT that favors the activated state.
• “Innate”, “Early”, or “primary” resistance are terms to describe patients in whom
progression is noted within 3–6 months of initiating imatinib.
• Early resistance: 20% of all patients.
• Seen with all mutations, but most often with KIT exon 9, PDGFRA, and WT.
• PDGFRA mutations are rare, and definite conclusions regarding response to
imatinib are difficult to make. Exon 12 and 14 are sensitive while D842V PDGFRA
mutations are resistant .
Molecular aspects for primary and secondary TKI
resistance in GIST (II) • “Delayed”, “Acquired”, or “Secondary” resistance :
progression of disease after an initial response or stable disease on imatinib .
Patients develop this resistance between 6 and 24 months of starting therapy
“late” (> 6 months) and “very late” (> 24 months)
• Secondary mutations are found in 50–70% of patients who progress and only in
patients with initial KIT/PDGFRA mutations, especially KIT exon 11.
• T670I “gatekeeper” is the most common secondary mutation. Other mutations are
in exon 14,17, and 18. No secondary mutations have been documented in wild-type
tumors.
• Major mechanisms of imatinib resistance are (1) secondary mutation in KIT or
PDGFRA in addition to the initial mutation, (2) overexpression of KIT as evidenced
by genomic amplification, (3) activation of alternate pathways and loss of KIT, and
(4) functional resistance, defined as mutations in regions of KIT or PDGFR that are
not bound by imatinib.
Model of GIST genomic progression • Most GISTs develop by stepwise accumulation of chromosomal aberrations
• 14q loss in 60-70% of early cases, 22q (50%), 1p (50%) and 15q (40%) in
intermediate and high risk tumors
• Homozygous deletion of tumor suppressor genes
Schafer IM, Nat Commun, 2017
MAX (myc-associated
factor X) inactivation
↓
p16 inactivation and cell
cycle perturbation
Later, inactivating
mutations of p53, RB1
Inactivation of
dystrophin encoded by
DMD gene is a late
event and occurs in
90% of metastatic
GISTs
• GIST : Introduction and History
• Morphology
• Molecular pathology, oncogenesis and prognosis
• Other rare spindle cell tumors of the GI tract and
differential diagnosis
Agenda
Mazur MT & Clark HB,
Am J Surg Pathol, 1983
Perez-Atayde AR
Am J Surg Pathol, 1993
Sarlomo-Rikala M, Mod Pathol, 1998
Hirota S, Science, 1998
Kindblom LG, Am J Pathol, 1998
Milestones