· PDF fileIf stopped to early- myasthenic crisis If overmedicated- cholinergic crisis. ... vs 47% without adjuvant RT,

www.downstatesurgery.org

Case Presentation HPI

62 year-old male presents with several episodes of anterior chest pain. Full cardiac evaluation was negative for ischemia. CT scan revealed a 4cm anterior mediastinal mass. Pt denies cough or respiratory issues. No weakness or diplopia.

PMHx: HTN, BPH, psychiatric disorder, negative cardiac stress test 4/2010

Allergies: NKDA

Meds: Lutensin, Atenolol, Norvasc, Fomax, Zyprexa, ASA 81

Shx: non-smoker


Case PresentationPhysical Exam

Afebrile, VSS

Pupils equal and reactive, no ptosis

No bruits, no lymphadenopathy

S1S2, RRR

Lungs clear bilaterally

Soft abd NT/ND, no inguinal LN’s

Labs

Hb/Hct: 13/39

Electrolytes- wnl

Coags- wnl

AChR-AB: negative


Chest Xraywww.downstatesurgery.org

CT scanwww.downstatesurgery.org

CT Scanwww.downstatesurgery.org

OR Procedure: Partial sternotomy, excision of thymic mass, partial

pericardectomy, partial excision of innominate vein with patch reconstruction

Pathology: Thymus- invasive squamous cell Ca of thymic origin Margins- all negative, except posterior (pericardial)- positive Positive lymphovascular invasion 2/9 LN positive for carcinoma T3, N1, Mx


Operative Procedurewww.downstatesurgery.org








Post-Operative Course Stable overnight stay in PACU on POD#0

Clears and OOB on POD#1 Chest tube output around 300 ml SSF

Chest tubes removed on POD# 3

Discharged Home on POD#5


Mediastinum Midline region between

the two lungs and their pleural coverings

• Occupied principally by heart, great vessels, trachea, bronchi, esophagus, and thymus

• Divided into Superior and Inferior (anterior, middle, and posterior)


Mediastinum Most common tumors of anterior superior mediastinum 4-T’s- thymoma, “terrible” lymphoma, teratoma and thyroid

lesions These represent more than 90% of all anterior mediastinal

masses

Posterior mediastinum DATES: Descending aorta, Azygous vein and hemiazygos

vein, Thoracic duct, Esophagus, Sympathetic trunk/ganglia

Thymoma is the most common mediastinal neoplasm in adults


Thymus A lymphoepithelial organ

derived embryologically from 3rd pair pharyngeal pouches that descend caudally and medially on the 7th week of life

By the 8th week the gland has fused to form a four-lobed gland attached to the anterior pericardium

Can be as cephalad as the hyoid bone or as far caudad as xiphoid process


Thymus Fully developed, it is a bilobed gland that sits in the

anterior mediastinum

It is separated from sternum by loose connective tissue, it lies anterior to pericardium and great vessels

It can extend laterally to phrenic nerves and is partially covered by the pleural reflections

It is in close contact to the left inomminate vein


Thymus Arterial supply Internal thoracic

(mammary)- main Inferior thyroid Pericardiophrenic

arteries

Venous drainage From both lobes, veins

ascend posteriorly into left brachiocephalic or rarely directly into SVC


Thymus Central lymphoid organ that transforms null lymphocytes

into thymic or T-lymphocytes, which are responsible for cellular immunity

Symptoms may arise from direct lesion compression or invasion, as well as from immunologic, hyperplastic or neoplastic manifestations


Thymoma Thymomas are epithelial tumors of the thymus 65% of thymomas are encapsulated (noninvasive) and 35%

are invasive.

Most common mediastinal neoplasm in adults, 40% of all anterior mediastinal masses

Most pts between ages 30-60 at diagnosis

Indolent growth pattern, but malignant due to its potential for local invasion, pleural dissemination and systemic metastases

1/3 of pts with localized dz are symptomatic: cough or chest pain


Thymoma Locally advanced or disseminated dz may present with

severe CP, SOB, phrenic n. paralysis, pleural effusions, and/or SVC syndrome

MG- most common autoimmune disorder associated with thymomas-ocurring in 30-40% of pts; 10% of MG pts have thymomas

Up to 30% of pts with thymoma present with other immune disorders- red cell aplasia and hypogammglobulinema


Diagnosis CT scan with IV contrast Defines size and relationship to intrathoracic structures Presence of droplet metastases- parietal pleural deposits

that are unique to thymomas

Differ from malignant nonseminomatous germ cell tumors Alpha feto protein (AFP) and B-HCG

Thyroid lesions are contiguous with thyroid gland on CT scan; I-131 nuclear scans to confirm


Droplet Metastaseswww.downstatesurgery.org

Diagnosis Two main DDx for anterior mediastinal mass Lymphoma and thymoma

Thymomas- older pts, association with immune disorder, no constitutional symptoms and no lymphadenopathy

Utility of PET scan for thymomas is being evaluated cannot differ between lymphoma and thymoma, but it can

identify droplet metastases


Diagnosis En bloc thymectomy for clinically determined early-stage

thymoma

For larger lesions FNA-lacks sensitivity CT guided core bx - seeding Anterior mediastinostomy Cervical mediastinoscopy VATS ( seeding)


Staging WHO classification based on histology Morphology and lymphocyte-to-epithelial ratio

Masaoka Anatomic classification Most accepted system on which management

recommendations are based


Staging Masaoka Anatomic classification Stage I: Macroscopically and microscopically encapsulated Stage II A- microscopic transcapsular invasion B- macroscopic invasion into surrounding fat or grossly adherent

but not through pleura or pericardium Stage III: Invasion into neighboring organs A- without invasion into great vessels B- with invasion of great vessels

Stage IV A- pleural or pericardial dissemination B- lymphogenous or hematogenous metastasis


Pre-op Assessment Anterior mediastinal mass (thymoma) H&P, AchR-AB assay, MuSKR-AB, EMG studies, TFTs, PFTs,

CXR, CT scan, and MRI

Pre-op optimization is crucial, especially when thymectomy is being done for MG Use pyridostigmine and immunosuppressive agents to

optimize strength and respiratory status Plasmapheresis or IVIG may help in pts with VC < 2L 22% of pts with pre-op respiratory insufficiency will require

long-term mechanical ventialation


Pre-op Assessment Major risk is weakness of oropharyngeal/respiratory

muscles, leading to aspiration, inability to cough and respiratory failure

Anticholinesterases (pyridostigmine) should be discontinued around 8hrs prior to surgery If stopped to early- myasthenic crisis If overmedicated- cholinergic crisis


Treatment Stage I/II: Complete en bloc thymectomy, and removal of all

surrounding fat with avoidance of phrenic n. or intrapleural spread

Median sternotomy provides excellent exposure and access

VATS- being done, long term follow up is needed to compare with open approaches


Treatment Difficult to establish a stage III before surgery

Unilateral phrenic n. resection can be done

Potentially operable stage III dz Induction chemotx- cisplatin based with response rates of

80-100%, and resectability rates bet 35-70% Post op radiation after stage III resection for local control

Stage IVa: induction chemotx, assess resectability; if not resectable- chemoradiation; steroids and octreotride as 2nd line


Thymoma Prognosis at 5 and 10 yrs

Stage I : 95%, 85%

Stage II: 80%, 75%

Stage III: 40-60%, 20-30%

Stage IV a: 0-40%


Thymic Carcinoma This tumor is a rare variant of thymic lesions and is

histologically and biologically different from invasive or malignant thymoma; these are malignant at microscopic level

Incidence: <1% of thymic malignancies, 5 year survival is 30-50%

Thymic carcinomas tend to be very invasive and difficult to resect completely

Even in the setting of complete resection, recurrence is common both locally and at distant sites

Typically, these are young men (< age 50 years) with an otherwise excellent performance status


Thymic Carcinoma PET scan better due to higher proliferative potential in

thymic carcinoma.

Aggressive combined-modality approach (induction chemotherapy, resection, and postoperative chemoradiotherapy) should be employed

While a good response to induction therapy and complete resection will provide a significant disease-free interval, long-term survival is still unlikely


Conclusion Goal of thymectomy should be complete removal of all

thymic tissue

MC indications: thymic neoplasm or MG

Thymoma should be resected because of its risk for invasive spread or morbidity due to mass effects

Even advanced tumors with local invasion of resectable structures such as the pericardium, superior vena cava, or innominate vessels should be considered for resection with reconstruction


Surgery is the cornerstone for thymic malignancies Complete resection is the most constant and significant

prognostic factor for progression-free and overall survival

Radiotherapy Although thymomas are regarded as being moderately

radiosensitive, controversy exists about its role as adjuvant therapy

Chemotherapy



Recommendations Stage I: Surgery to obtain microscopically complete

resection

Stage II-III (resectable): Surgery, post op RT controversial, but clearly recommended for incompletely resected tumors Increased Mediastinal recurrence-free survival from 0-79%

vs 47% without adjuvant RT, No increase in overall survival


Recommendations Stage III-IV a (marginally resectable): Surgery and post-op

radiation therapy, perioperative chemotherapy in incomplete resection (Level 2C evidence) Debulking surgery in debate, survival rates only 5-10%

Stage III-IV a (initially unresectable) Upfront chemotherapy followed by surgery or radiation

therapy depending on whether sufficient down-staging has been achieved.

Stage IVB Chemotherapy is treatment of choice typically multiple

agents.


Recommendations

Local and Locoregional recurrences of thymoma Late recurrences 5-10 year are not uncommon In cases of recurrent thymoma, surgery remains the

mainstay in therapy In nonresectable local recurrences, exclusive

radiotherapy has been reported as an efficient treatment.


Key Points Tumors of the thymus represent a wide spectrum of

diseases; Thymoma predominates

Surgeon’s role- knowledge of differential diagnoses, associated symptoms, palpable lymphadenopathy

Pre-op management

Surgery is the mainstay of therapy and obtaining complete resection is the most important prognostic factor

Due to its rarity, further studies are warranted to evaluate and improve current therepeutic standards.


References Alavi A, Gupta N, Alberini JLPositron emission tomography imaging in

nonmalignant thoracic disorders. Sem Nucl Med 2002; 22:293.and others

Kelemen 3rd JJ, Naunheim KS: Minimally invasive approaches to mediastinal neoplasms. Sem Thorac Cardiovasc Surg 2000; 12:301.

Kim ES, Putnam JB, Komaki R: Phase II study of a multidisciplinary approach with induction chemotherapy, followed by surgical resection, radiation therapy, and consolidation chemotherapy for unresectable malignant thymomas. Lung Cancer 2004; 44:369.and others

Wright CD, Kessler KA: Surgical treatment of thymic tumors. Sem Thorac Cardiovasc Surg 2005; 17:20.



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