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Mediastinum

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Germ cell tumors

Author: Hanni Gulwani, M.B.B.S.

Last author update: 1 December 2012

Last staff update: 15 March 2023 (update in progress)

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PubMed Search: Germ cell tumors mediastinum

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Table of Contents

Cite this page: Gulwani H. Germ cell tumors. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/mediastinumgermcell.html. Accessed June 9th, 2023.

Definition / general

20% of mediastinal tumors and cysts
Typically divided into seminomas versus nonseminomatous germ cell tumors (teratomas [mature or immature], embryonal carcinomas, yolk sac tumors and choriocarcinoma) (Rev Pneumol Clin 2010;66:63)
Malignant transformation of germinal elements without a gonadal focus (Rev Assoc Med Bras 2006;52:182)

Epidemiology

Usually males ages 20 - 49 years, similar to gonadal tumors (Cancer 1997;80:681)

Clinical features

Mediastinal tumor in 20 - 49 year old man should be presumed to be a germ cell tumor until proven otherwise
Often elevated serum AFP, hCG, HPL, LDH, PLAP
Associated with i(12p)+ acute leukemia, Klinefelter syndrome (30x risk)
Nonteratomas are often very large at diagnosis

Prognostic factors

May have aggressive behavior if not limited to mediastinum at diagnosis (Cancer 1997;80:699, Pediatr Hematol Oncol 2012;29:633)
Prognosis worse than gonadal germ cell tumors; 5 year disease free survival is 50 - 65% for seminomas, 20% for other subtypes
Sarcomatous component is poor prognostic sign (Am J Surg Pathol 2007;31:1356)
Good prognostic factors for nonseminomatous tumors: rapid decline in serum AFP or hCG after surgery and chemotherapy, no vascular invasion, no yolk sac or choriocarcinoma components

Gross description

Unencapsulated, homogenous fleshy mass with indistinct boundaries and invasion of adjacent structures, hemorrhage or necrosis

Cytology description

Fine needle aspiration biopsy can establish diagnosis with high degree of accuracy (Am J Clin Pathol 2002;118:418)

Differential diagnosis

Metastatic germ cell tumor:
- Unlikely if single tumor with no retroperitoneal involvement

Choriocarcinoma

Epidemiology

Usually men in 20s with elevated hCG and gynecomastia, impotence

Prognostic factors

Poor prognosis

Case reports

13 year old boy with shortness of breath, chest pain, fever, irritable cough and weight loss (Zhongguo Dang Dai Er Ke Za Zhi 2009;11:517)
14 year old boy with placental site trophoblastic tumor (Hum Pathol 2005;36:581)
25 year old man with choriocarcinoma masquerading as relapsed Hodgkin lymphoma (Case Rep Oncol 2011;4:512)
25 year old man with concurrent development of testicular seminoma and choriocarcinoma of superior mediastinum, presenting as cervical mass (BMC Clin Pathol 2006;6:8)

Microscopic (histologic) description

Mixed proliferation of syncytiotrophoblasts (large, atypical multinucleated cells with abundant eosinophilic cytoplasm, bizarre nuclei, prominent nucleoli) and cytotrophoblasts (clear cytoplasm, uniform round nuclei, prominent nucleoli, numerous atypical mitoses)

Microscopic (histologic) images

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Resemble Reed-Sternberg cells

CAM5.2+

Diffuse
cytotrophoblasts,
syncytiotrophoblasts
are β hCG+

Cytology images

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Transbronchial aspirate: syncytiotrophoblast

Positive stains

Keratin, EMA, hCG

Electron microscopy description

Cytoplasmic tonofibrils and plasmalemmal microvilli

Differential diagnosis

Metastasis from occult testicular primary:
- Clinical history required

Embryonal carcinoma

Epidemiology

Usually males

Gross description

Invasive, highly necrotic

Microscopic (histologic) description

Poorly differentiated, pleomorphic cells with prominent nucleoli, often with eosinophilic intracellular globules or primitive lumina; variable geographic necrosis
No nuclear blebs

Microscopic (histologic) images

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Primitive polygonal cells

Immunostains

Positive stains

Keratin, OCT3 / 4, c-kit, CD30; variable AFP and PLAP

Negative stains

EMA, CD45, CEA, S100, muscle specific actin

Electron microscopy description

Well developed junctional complexes, complex nucleoli, primitive microvillous structures or intracellular lumina

Molecular / cytogenetics description

i(12p)

Germ cell tumor - mixed

Definition / general

Common, describe individual components present and percentage of each

Case reports

67 year old man with primary embryonal carcinoma and choriocarcinoma (Arch Pathol Lab Med 1982;106:507)

Cytology images

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Metastatic tumor

Seminoma

Epidemiology

Almost always males

Sites

Thymus

Prognostic factors

5 year disease free survival is 50 - 65%; 10 year actuarial survival is 69%
Good prognostic factors: age 35 years or less at diagnosis, no superior vena caval syndrome, no mediastinal lymphadenopathy, no fever

Case reports

25 year old man with superior vena cava syndrome (Intern Med 2012;51:1269)
28 year old man with Down syndrome (J Pediatr Hematol Oncol 2012;34:387)

Treatment

Excision, radiation therapy

Gross description

Solid, homogenous, tan-white bulging cut surface, residual thymic tissue may be present

Microscopic (histologic) description

Nests of large tumor cells with clear cytoplasm (due to glycogen), distinct cell membranes, prominent nucleoli, separated by fibrous stroma with abundant lymphocytes
Often epithelioid granulomas, numerous germinal centers, variable geographic necrosis, no nuclear blebs
May entrap normal thymus cells

Microscopic (histologic) images

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Thymic seminoma

Positive stains

CAM5.2 (dot-like paranuclear pattern in 80%), PLAP (membranous in only 50%) - pattern is different from testicular tumors (Hum Pathol 1998;29:737)
Also PAS, CD57 / Leu7

Negative stains

EMA, LCA, CEA, S100, muscle specific actin

Electron microscopy description

Primitive appositional intercellular junctions, prominent and complex nucleoli (nucleolonemata), abundant cytoplasmic glycogen, no premelanosomes, no complex branching microvilli

Differential diagnosis

Teratoma - immature

Definition / general

Teratoma with immature epithelial, mesenchymal or neural elements

Clinical features

Extragonadal germ cell tumors in children are uncommon and occasionally present with atypical features (J Indian Assoc Pediatr Surg 2012;17:9)

Prognostic factors

Good prognosis if 14 years old or less

Case reports

9 year old girl with chest pain and respiratory distress (Indian J Pathol Microbiol 2006;49:32)

Gross images

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Excised tumor with rib

Microscopic (histologic) images

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Primitive glomeruli

Cartilage and ossification

Teratoma - mature

Definition / general

Most common mediastinal germ cell neoplasm
Benign
Peripheral eggshell calcifications in anterior mediastinal mass are relatively specific
Often adheres to surrounding structures

Sites

May perforate trachea / bronchi, causing patient to cough up hair and oily / sebaceous material

Case reports

22 year old man whose tumor compressed right atrium (J Med Case Rep 2011;5:193)
28 year old woman with coexisting mediastinal and ovarian teratoma (J Thorac Dis 2012;4:434)
35 year old woman with carcinoid arising in mature teratoma (Asian Cardiovasc Thorac Ann 2012;20:80)
44 year old man with adenocarcinoma with sarcomatous dedifferentiation arising from mature cystic teratoma (Pathol Res Pract 2012;208:741)

Treatment

Xanthogranulomatous reaction if sebaceous material escapes

Microscopic (histologic) description

Cysts lined by stratified squamous material with sebaceous glands and hair follicles
Also cartilage, GI, pancreatic tissue, respiratory structures; may have mature neural tissue

Microscopic (histologic) images

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