Mediastinum

Other tumors

Germ cell tumors



Last staff update: 19 January 2024 (update in progress)

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PubMed Search: Germ cell tumors mediastinum

Sarosh Moeen, M.B.B.S.
Rashida Ahmed, M.B.B.S.
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Cite this page: Moeen S, Chundriger Q, Ahmed R. Germ cell tumors. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/mediastinumgermcell.html. Accessed February 22nd, 2024.
Definition / general
  • Account for 1 - 15% of all mediastinal neoplasms in adults and 11 - 20% in children (J Thorac Oncol 2020;15:568, Ann Surg Oncol 1994;1:121)
  • Classified as seminomas and nonseminomatous germ cell tumors (yolk sac tumor, embryonal carcinoma, choriocarcinoma, teratoma and mixed germ cell tumor)
  • A seminoma with any component of a nonseminomatous tumor is considered a nonseminomatous germ cell tumor
Essential features
  • Mature teratomas and yolk sac tumors are almost exclusively the tumor types in very young patients
  • Seminomas are almost always diagnosed in patients ≥ 10 years old
  • Mixed mediastinal germ cell tumors more common in adults
  • Majority occur in anterior mediastinum
  • On CT, presence of fat is suggestive of their presence; however, fat fluid level or bone is pathognomonic of teratoma
  • Immunoprofile of primary mediastinal germ cell tumors is similar to their gonadal counterparts
Terminology
  • Seminoma
  • Nonseminomatous germ cell tumors (NSGCT) include yolk sac tumor, embryonal carcinoma, choriocarcinoma, teratoma and mixed germ cell tumor
ICD coding
  • ICD-O:
    • 9061/3 - seminoma
    • 9070/3 - embryonal carcinoma
    • 9071/3 - yolk sac tumor
    • 9100/3 - choriocarcinoma
    • 9080/0 - mature teratoma
    • 9080/1 - immature teratoma of the thymus
    • 9085/3 - mixed germ cell tumor
    • 9084/3 - teratoma with somatic type malignancies
    • 9086/3 - germ cell tumor with associated hematological malignancy
Epidemiology
  • Median age of mediastinal seminoma is 33 years, while NSGCT is 28 years (J Clin Oncol 2002;20:1864)
  • Mature teratomas and yolk sac tumors are almost exclusively the tumor types in very young patients
  • Seminomas are almost always diagnosed in patients aged ≥ 10 years (Pediatr Blood Cancer 2004;42:169)
  • Mixed mediastinal germ cell tumors more common in adults
  • M > F (Front Oncol 2020;10:1137)
  • Benign teratomas have equal gender distribution
Sites
Pathophysiology
  • Thought to arise from aberrant migration of primitive germ cells during embryonic development or from stem cells in thymus (Int J Androl 2007;30:256)
Etiology
Diagrams / tables

Gross, micro, IHC and serum markers of germ cell tumors
Tumor type Gross features Microscopic features Serum markers Pankeratin SALL4 OCT3/4 CD30 Glypican 3 Beta hCG CD117
Teratoma Solid combined with cystic, Rokitansky protuberans contains shiny cartilage, hair and teeth, etc. Derivatives of all 3 germinal layers Beta hCG: normal
LDH: normal
AFP: normal
Positive in epithelial elements Negative in mature components Negative in mature components Negative Negative Negative Negative
Embryonal carcinoma Gray-white with areas of hemorrhage and necrosis Sheets and aggregates of highly pleomorphic cells Beta hCG: normal
LDH: raised
AFP: raised
Positive Positive Positive Positive Negative Negative Negative
Yolk sac tumor Gray-white with variable hemorrhage Numerous growth patterns, Schiller-Duval bodies, eosinophlic globules Beta hCG: normal
LDH: normal
AFP: raised
Positive Positive Negative Negative Positive Positive in syncytio-trophoblasts Negative
Chorio-carcinoma Markedly hemorrhagic Trimorphic population of trophoblasts with extensive hemorrhage Beta hCG: raised
LDH: normal
AFP: normal
Positive Negative Negative Negative Negative Positive in syncytio-trophoblasts Negative
Seminoma Gray-white, shiny cut surface Islands of pleomorphic cells with prominent nucleoli, separated by thin fibrous septa having lymphocytes Beta hCG: raised
LDH: raised
AFP: normal
Negative Positive Positive Negative Negative Negative Positive
Clinical features
  • Chest pain, cough, dyspnea, superior vena cava syndrome, weight loss, cervical mass, chest wall mass
  • Lung involvement, liver and bone metastasis (Front Oncol 2020;10:1137)
Diagnosis
  • Clinical symptoms and elevated serum markers
  • Radiological examination indicating a mass most commonly in anterior mediastinum
Laboratory
  • Lactate dehydrogenase (LDH)
  • Alpha fetoprotein (AFP)
  • Beta human chorionic gonoadotropin (hCG)
Choriocarcinoma
Definition / general
  • Highly malignant trophoblastic neoplasm composed of syncytiotrophoblasts, cytotrophoblasts and variable number of intermediate trophoblasts

Essential features

ICD coding
  • ICD-O: 9100/3 - choriocarcinoma
  • ICD-11: 2C28.0 & XH8PK7 - malignant germ cell neoplasms of heart, mediastinum or nonmesothelioma of pleura & choriocarcinoma, NOS

Epidemiology
Sites

Etiology
Clinical features
Diagnosis
  • Radiological imaging with serum markers and biopsy or excision

Laboratory
  • Elevated serum beta hCG levels

Radiology description
Radiology images

Images hosted on other servers:

Mediastinal mass & metastatic lung nodules

Mass in posterior mediastinum



Prognostic factors
Case reports
  • 25 year old man presented with cutaneous metastasis of primary mediastinal choriocarcinoma (J Cutan Pathol 2021;48:81)
  • 26 year old man with primary mediastinal choriocarcinoma with diffuse metastasis to both lungs and multiple brain metastases (Medicine (Baltimore) 2019;98:e16411)
  • 71 year old man on goserelin treatment for metastatic prostatic adenocarcinoma developed mediastinal choriocarcinoma with lung and vertebral metastases (Case Rep Pathol 2019;2019:2734815)

Treatment
  • Chemotherapy, radiotherapy and surgery
  • Treatment with cisplatin based therapy may improve the outcome

Gross description
  • Large, soft, friable, extensively hemorrhagic and with foci of necrosis

Microscopic (histologic) description
  • Intermingled syncytiotrophoblasts and cytotrophoblasts in a plexiform pattern or in disordered sheets
  • Syncytiotrophoblasts, large multinucleated cells with numerous, pleomorphic, dark staining nuclei, variably distinct nucleoli and abundant densely eosinophilic or amphophilic cytoplasm
  • Cytotrophoblasts, uniform, polygonal cells with round nuclei, prominent nucleoli and clear or eosinophilic cytoplasm
  • Dilated vascular sinusoids
  • Extensive areas of hemorrhage and necrosis
  • Atypical mitoses and cellular atypia are common (J Cutan Pathol 2021;48:81, Mediastinum 2019;3:30)
  • Mostly choriocarcinoma occurs as a component of mixed germ cell tumors (Arch Pathol Lab Med 2019;143:65)

Microscopic (histologic) images

Contributed by Sarosh Moeen, M.B.B.S.
Intermediate sized cells

Intermediate sized cells

Pankeratin (CK AE1 / AE3)

Pankeratin (CK AE1 / AE3)



Cytology description
  • Abundant necrosis and hemorrhage with clusters or isolated multinucleated syncytiotrophoblasts

Cytology images

Images hosted on other servers:

Transbronchial aspirate: syncytiotrophoblast



Positive stains
Negative stains
Sample pathology report
    • Anterior mediastinal mass, core biopsy:
      • Germ cell tumor with morphological and immunohistochemical profile favoring choriocarcinoma (see comment)
      • Comment: A possibility of mixed germ cell tumor in the vicinity cannot be excluded.

    Differential diagnosis
    • Sarcomatous carcinoma with giant cells:
      • Shows small to medium sized tumor cells with larger giant cells; this is in contrast with choriocarcinomas that show 2 cell populations of cytotrophoblasts and syncytiotrophoblasts
Embryonal carcinoma
Definition / general
  • Malignant nonseminomatous germ cell tumor characterized by embryonal type cells

ICD coding
  • ICD-O: 9070/3 - embryonal carcinoma
  • ICD-11: 2C28.0 & XH8MB9 - malignant germ cell neoplasms of heart, mediastinum or nonmesothelioma of pleura & embryonal carcinoma, NOS

Epidemiology
  • Accounts for 2 - 8% of primary mediastinal germ cell tumors (Cancer 2003;97:367)
  • Predominantly in young males

Sites
  • Occurs in anterior mediastinum

Etiology
  • Same as other nonseminomatous germ cell tumors

Clinical features
  • Chest pain, dyspnea, cough and superior vena cava syndrome

Diagnosis
  • Mediastinal mass on radiology and subsequent biopsy

Laboratory
  • Elevated LDH and AFP levels

Radiology description
  • Large, lobulated, heterogeneous mass with hemorrhage, necrosis and calcifications on CT scan
  • On MRI, cystic or necrotic areas appear hyperintense on T2 weighted images
  • FDG PET useful in evaluation of recurrent disease or residual viable tumor after chemotherapy (AJR Am J Roentgenol 2010;195:W274)

Radiology images

Images hosted on other servers:

Expansion of tumor; heterogeneously enhanced



Prognostic factors
Case reports
  • 12 year old boy with large soft tissue mass in mediastinum and left thoracic cavity, diagnosed as malignant mixed germ cell tumor with yolk sac tumor, immature teratoma and embryonal carcinoma components (Open Med (Wars) 2021;16:892)
  • 23 year old man with anterior mediastinal mass and right pleural effusion developed pericardial effusion and cardiac tamponade (AJR Am J Roentgenol 1998;170:722)
  • 25 year old man with an unresectable embryonal carcinoma of the anterior mediastinum that developed a bronchial fistula after systemic chemotherapy (Case Rep Radiol 2020;2020:7650206)
  • 29 year old man with primary mediastinal embryonal carcinoma presented with pulmonary artery stenosis (Pneumonol Alergol Pol 2015;83:151)

Treatment
Gross description
  • Infiltrating and large with size up to 22 cm
  • Hemorrhagic and necrotic cut surface

Microscopic (histologic) description
  • Large and polygonal cells sometimes columnar with indistinct cell borders
  • Eosinophilic, amphophilic, basophilic or clear cytoplasm
  • Nuclei have large single or multiple nucleoli (Histopathology 2022;80:381)
  • Numerous mitoses, often atypical
  • Solid, tubular / glandular or papillary growth patterns
  • Tumor necrosis is common (Mediastinum 2019;3:30)

Microscopic (histologic) images

Contributed by Sarosh Moeen, M.B.B.S.
Islands of tumor cells

Islands of tumor cells

Pleomorphic cells

Pleomorphic cells

Pankeratin CK AE1 / AE3

Pankeratin CK AE1 / AE3

SALL4

SALL4


OCT3/4

OCT3/4

Glypican 3

Glypican 3

CD30

CD30



Cytology description
  • Syncytial cohesive clusters of pleomorphic cells with frequent mitoses
  • Necrosis and hemorrhage in many cases (Cancer 2008;114:504)

Cytology images

Images hosted on other servers:

Pleomorphic tumor cells; marked nuclear pleomorphism



Positive stains
Negative stains
Sample pathology report
  • Anterior mediastinal mass, core biopsy:
    • Germ cell tumor with morphological and immunohistochemical profile favoring embryonal carcinoma (see comment)
    • Comment: A possibility of mixed germ cell tumor in the vicinity cannot be excluded.

Differential diagnosis
Mixed germ cell tumors of the mediastinum
Definition / general
  • Neoplasms composed of 2 or more types of germ cells

Essential features
  • Presence of more than 1 type of germ cell tumor

Terminology
  • Malignant teratoma (not recommended)

ICD coding
  • ICD-O: 9085/3 - mixed germ cell tumor
  • ICD-11: 2C28.0 & XH2PS1 - malignant germ cell neoplasms of heart, mediastinum or nonmesothelioma of pleura & mixed germ cell tumor

Epidemiology
  • In adults, M > F and common tumor components are teratoma and embryonal carcinoma
  • In children, yolk sac tumor and teratoma (mature or immature) are the most common types

Sites
  • Occur in anterior mediastinum

Etiology
  • Similar to other types

Clinical features
  • Mediastinal mass and elevated serum markers

Diagnosis
  • Elevated serum markers
  • Mediastinal mass on imaging
  • Biopsy showing 2 or more types of germ cell components

Laboratory

Radiology description

Radiology images

Images hosted on other servers:
CT scan of chest with anterior mediastinal mass


CT scan of chest with anterior mediastinal mass



Case reports
  • 12 year old boy with mixed germ cell tumor of the mediastinum diagnosed on core biopsy (Open Med (Wars) 2021;16:892)
  • 16 year old boy with huge mediastinal mass diagnosed as mixed germ cell tumor with possible combination of embryonal carcinoma, yolk sac and teratoma (Case Rep Surg 2016;2016:7615029)
  • 26 year old man with mixed germ cell tumor comprising of immature teratoma and seminoma diagnosed due to massive organ displacing tumor in right chest on chest Xray (Pathol Res Pract 2009;205:572)
  • 29 year old man with disease progression despite systemic chemotherapy, diagnosed as mixed germ cell tumor on en bloc resection (J Surg Case Rep 2021;2021:rjab416)

Treatment
  • Resected after chemotherapy

Gross description
  • Heterogeneous cut surface
  • Solid, fleshy tumor with areas of hemorrhage and necrosis
  • Cystic spaces indicate presence of a teratomatous component

Gross images

Images hosted on other servers:
4.6 kg mediastinal mixed germ cell tumor, mostly teratoma

4.6 kg mediastinal mixed GCT, mostly teratoma



Microscopic (histologic) description
  • Morphology identical to pure germ cell component
  • Please refer to the sections above for microscopic description of individual components

Cytology description
  • Please refer to the sections above for cytological description of individual components

Positive stains
  • Please refer to the sections above for individual components

Negative stains
  • Please refer to the sections above for individual components

Sample pathology report
  • Anterior mediastinal mass, biopsy:
    • Malignant mixed germ cell tumor with seminoma (~50%), yolk sac tumor (~30%) and embryonal carcinoma (~20%) components (see comment)
    • Comment: The findings show majority of tumor comprised of sheets of polygonal cells with vesicular nuclei and prominent nucleoli. Intervening fibrous septa show lymphocytic infiltration. This component stains positive for immunohistochemical stains SALL4 and OCT3/4 while staining negative for CD30 and glypican 3. Another admixed component shows reticular pattern and Schiller-Duval bodies of cuboidal cells which stain positive for SALL4 and glypican 3 while staining negative for OCT3/4 and CD30. A small component comprised of large polygonal cells with pleomorphic nuclei, prominent nucleoli, numerous mitoses and necrosis is seen. This component stains positive for SALL4 and OCT3/4 and CD30 while staining negative for glypican 3.
    • See synoptic reporting for resection specimen.
Seminoma
Definition / general
  • Malignant germ cell tumor composed of seminomatous germ cells
  • A seminoma with any component of a nonseminomatous tumor is considered a nonseminomatous germ cell tumor (NSGCT)

Essential features

Terminology
  • Germinoma

ICD coding
  • ICD-O: 9061/3 - seminoma
  • ICD-11: 2C28.0 & XH9FM4 - malignant germ cell neoplasms of heart or mediastinum, or nonmesothelioma of pleura & seminoma, NOS

Epidemiology
Sites

Etiology
Clinical features
  • Most patients are symptomatic
  • Dyspnea, chest pain, superior vena cava syndrome, cough with hemoptysis, hoarseness

Diagnosis
Laboratory
Radiology description
Radiology images

Images hosted on other servers:

Mass (M) in prevascular mediastinum



Prognostic factors
  • Prognosis is better than nonseminomatous malignant germ cell tumors
  • Good prognosis if nonpulmonary visceral metastasis is absent (J Clin Oncol 2002;20:1864)

Case reports
Treatment
  • Cisplatin based combination chemotherapy and radiotherapy
  • Surgical excision is reserved for cases not responding to chemotherapy and radiotherapy (Oncol Res Treat 2019;42:95)

Gross description
  • Smooth and glistening or lobulated outer surface
  • Soft, creamy to light tan nodular cut surfaces (Kaohsiung J Med Sci 2005;21:395)
  • May show both solid and cystic areas with necrotic material

Gross images

Images hosted on other servers:

Cystic seminoma with necrotic tissue



Microscopic (histologic) description
  • Round to polygonal, uniform epithelioid cells with round to oval nuclei, vesicular chromatin and large nucleoli
  • Abundant, glycogen rich, clear to lightly eosinophilic cytoplasm and distinct cell membranes
  • Tumor cells grow in confluent sheets, multinodular clusters, cords or irregular lobules
  • Lymphocytic infiltration of fibrous septa / stroma is almost always seen
  • Other findings including nonnecrotizing granulomas, cellular pleomorphism, necrosis, intercellular edema, syncytiotrophoblasts (Kaohsiung J Med Sci 2005;21:395, Int J Clin Exp Pathol 2019;12:3082)

Microscopic (histologic) images

Contributed by Sarosh Moeen, M.B.B.S.
Uniform appearing cells

Uniform appearing cells



Cytology description
  • Discohesive cells, round or polygonal nuclei, 1 or more prominent nucleoli, pale cytoplasm
  • Lymphocytes, plasma cells and characteristic tigroid stripes
  • Necrosis and giant cells may be present (Cancer 2008;114:504)

Cytology images

Images hosted on other servers:

Clusters of cells; tigroid background

Cytologic smear; cell block



Positive stains
Negative stains
Sample pathology report
  • Anterior mediastinal mass, core biopsy:
    • Germ cell tumor with morphological and immunohistochemical profile favoring seminoma (see comment)
    • Comment: A possibility of mixed germ cell tumor in the vicinity cannot be excluded.

Differential diagnosis
Teratoma
Definition / general
  • Neoplasm of pluripotent cell origin that forms differentiated somatic type tissues, which may be exclusively mature (adult type), exclusively immature (embryonal or fetal) or a combination of both

Essential features
  • Tumor composed entirely of differentiated somatic type tissue, may be mature, immature or combined

ICD coding
  • ICD-O:
    • 9080/0 - mature teratoma
    • 9080/1 - immature teratoma of the thymus
  • ICD-11:
    • 2C28.0 & XH3GV5 - malignant germ cell neoplasms of heart, mediastinum or nonmesothelioma of pleura & teratoma, benign
    • 2C28.0 & XH7YZ9 - malignant germ cell neoplasms of heart, mediastinum or nonmesothelioma of pleura & teratoma, malignant, NOS

Epidemiology
Sites
  • Occurs in anterior mediastinum and rarely in posterior mediastinum

Etiology
  • Limited data about molecular biology and genetic features of primary mediastinal teratomas

Clinical features
  • Chest pain, shortness of breath, wheezing and cough due to compression of adjacent structures
  • Superior vena cava syndrome, hemoptysis, dysphagia, nausea and hoarseness are less common

Diagnosis
  • Incidental mass on radiological imaging in asymptomatic patients with serum tumor markers (AFP and beta hCG) not elevated
  • More symptomatic in children
  • Characteristic radiological findings of soft tissue, fat, fluid and calcifications in variable proportions
  • Biopsy findings showing differentiated somatic type tissue, may be mature, immature or combined

Laboratory
  • Serum tumor markers AFP and beta hCG are not elevated

Radiology description
Radiology images

Images hosted on other servers:

Huge posterior mediastinal mass

Anterior mediastinal mass



Prognostic factors
  • Mature teratomas are benign
  • Immature teratomas have malignant potential and malignant behavior correlates with amount of immature tissue
  • Somatic type malignancy may occur in mature teratomas, which determines the prognosis (Int J Surg Case Rep 2021;80:105680)

Case reports
Treatment
  • Complete surgical excision in cases of benign teratoma

Clinical images

Images hosted on other servers:

En bloc tumor resection



Gross description
  • Encapsulated masses with variegated cut surface and unilocular or multilocular cysts
  • Cyst contents may include clear fluid, mucoid material, sebaceous and keratinaceous debris, hair, fat, cartilage and rarely teeth or bone
  • Immature teratomas have soft to fleshy consistency or are extensively fibrous or cartilaginous
  • Hemorrhage and necrosis common

Gross images

Images hosted on other servers:

Excised tumor with rib



Microscopic (histologic) description
  • Haphazard distribution of mature somatic tissue is hallmark
  • Skin and cutaneous appendages are common, often lining cysts
  • Bronchial mucosa, glands, gastrointestinal mucosa, nerves and mature brain tissue
  • Smooth muscle, adipose tissue, mature pancreatic tissue
  • Immature tissue corresponds to embryonal or fetal tissues either exclusively or in addition to mature tissue
  • Most common immature tissue is neuroectodermal tissue with neuroepithelial cells forming tubules and rosettes (Mediastinum 2019;3:30)
  • Fetal lung, mesenchyme, primitive cartilage, bone, rhabdomyoblasts may be seen

Microscopic (histologic) images

Contributed by Sarosh Moeen, M.B.B.S.
Skin and choroid plexus

Skin and choroid plexus

Mucinous epithelium

Mucinous epithelium

Respiratory and squamous epithelium

Respiratory and squamous epithelium

Glial tissue

Glial tissue

Mature bone

Mature bone


Cartilage lobule

Cartilage lobule

Adipose tissue and acini

Adipose tissue and acini

Odontogenic tissue

Odontogenic tissue

Pancreatic acini

Pancreatic acini



Cytology description
  • Anucleate squamous cells and macrophages in a cystic background
  • Presence of ciliated bronchial epithelium, smooth muscle and cartilage may be mistaken for contamination
  • Presence of pancreatic acini or intestinal type mucosa may be suggestive of a teratomatous lesion
  • Careful correlation with imaging and serological studies to exclude mixed germ cell tumor (Cancer 2008;114:504)

Cytology images

Images hosted on other servers:

Mature and immature teratoma



Positive stains
  • Not supportive in mature teratoma

Negative stains
Videos

Pathology mini tutorial for teratoma



Sample pathology report
  • Anterior mediastinal mass, core biopsy:
    • Germ cell tumor with features favoring mature teratoma (see comment)
    • Comment: The microscopic features show skin adnexal structures, mature cartilage and a tiny focus of mature glial tissue.
    • A possibility of immature component or mixed germ cell tumor in the vicinity cannot be excluded.

Differential diagnosis
Yolk sac tumor
Definition / general
  • Malignant nonseminomatous germ cell tumor characterized by numerous patterns that recapitulate the yolk sac, allantois and extraembryonic mesenchyme

Terminology
  • Endodermal sinus tumor (not recommended)

ICD coding
  • ICD-O: 9071/3 - yolk sac tumor
  • ICD-11: 2C28.0 & XH09W7 - malignant germ cell neoplasms of heart, mediastinum or nonmesothelioma of pleura & yolk sac tumor

Epidemiology
  • Restricted to males after puberty and strong female preponderance in children
  • Peak incidence at third decade of life in adults
  • Pure yolk sac tumor 2 - 12% of mediastinal germ cell tumor in adults
  • Yolk sac tumor is virtually the only malignant germ cell tumor of the mediastinum in children up to 5 years of age (Turk Pediatri Ars 2019;54:185, Ann Diagn Pathol 2021;53:151763)

Sites
  • Most commonly anterior mediastinum

Etiology
  • Klinefelter syndrome is a risk factor after puberty (Int J Pediatr Endocrinol 2020;2020:18)
  • Genetic losses at 1p, 4q and 6q and gains at 1q, 3, 20q and 20 reported in mediastinal yolk sac tumors in patients < 8 years of age
  • After 8 years of age, isochromosome 12p, gain of chromosome 21 and X and loss of chromosome 13

Clinical features
  • Chest pain, dyspnea, chills, fever and superior vena cava syndrome

Diagnosis
  • FDG PET may detect tiny occult primary tumor or recurrences

Laboratory
Radiology description
  • Large solid - cystic mass with intratumoral hemorrhage, capsular tear, marked heterogeneous enhancement and enlarged intratumoral vessels on CT scan (Acta Radiol 2016;57:98)

Radiology images

Images hosted on other servers:

CT scan of chest



Prognostic factors
  • No significant difference between yolk sac tumor and mixed germ cell tumor
  • Complete surgical resection is the most favorable prognostic factor

Case reports
Treatment
Gross description
  • Solid or cystic with soft pale gray cut surface and gelatinous or mucoid consistency
  • Hemorrhage and necrosis after neoadjuvant therapy
  • Cyst formation may be treatment related or may indicate a mixed germ cell tumor

Gross images

Images hosted on other servers:

Firm, solid white mass



Microscopic (histologic) description
  • Different histologic patterns: microcystic (reticular), macrocystic, glandular - alveolar, endodermal sinus (pseudopapillary), myxomatous, hepatoid, enteric, polyvesicular - vitelline, solid and spindle
  • Loose network of cystic spaces and channels lined by flat or cuboidal cells with scant cytoplasm in a microcystic / reticular pattern
  • Pseudopapillary structures and Schiller-Duval bodies in endodermal sinus pattern (Kaohsiung J Med Sci 2005;21:395)
  • Cysts lined by cuboidal to flat tumor cells surrounded by dense fibrous stroma in a polyvesicular / vitelline pattern (Mediastinum 2019;3:30)
  • Solid pattern resembles seminoma and embryonal carcinoma

Microscopic (histologic) images

Contributed by Sarosh Moeen, M.B.B.S.
Sheet-like growth of cells

Sheet-like growth of cells

Marked pleomorphism

Marked pleomorphism

SALL4

SALL4

OCT3/4

OCT3/4

Glypican 3

Glypican 3



Cytology description
  • Aggregates of medium to large cells with variable nuclei and prominent nucleoli
  • Cytoplasm moderate to abundant
  • Background debris or mucoid material
  • Presence of hyaline globules is typical (Cancer 2008;114:504)

Cytology images

Images hosted on other servers:

Pap; Giemsa



Positive stains
Negative stains
Sample pathology report
  • Anterior mediastinal mass, core biopsy:
    • Germ cell tumor with immunohistochemical profile favoring yolk sac tumor (see comment)
    • Comment: A possibility of mixed germ cell tumor in the vicinity cannot be excluded.

Differential diagnosis
Board review style question #1

A 35 year old man presented with signs and symptoms of superior vena cava syndrome. On radiology, a mass was found in the anterior mediastinum, pushing on to the great vessels. It was resected. The photomicrograph above shows the histologic features. The tumor stained with SALL4 and OCT3/4 and was negative for CD30. What is the most likely diagnosis in this case?

  1. Embryonal carcinoma
  2. Seminoma
  3. Teratoma
  4. Yolk sac tumor
Board review style answer #1
B. Seminoma. The microscopic image shows sheets of tumor cells with fibrous septa infiltrated by lymphocytes. The cells are round to polygonal, uniform epithelioid cells with round to oval nuclei and vesicular chromatin. These features plus the IHC pattern are typical for seminoma. The morphology is not typical for the other germ cell tumors. Answer A is incorrect because embryonal carcinoma is positive for CD30 in addition to the other 2 markers given. Answer C is incorrect because teratoma is negative for all 3 markers. Answer D is incorrect because yolk sac tumor shows only SALL4 positivity. Therefore, the correct answer is seminoma.

Comment Here

Reference: Germ cell tumors
Board review style question #2
A 24 year old man presented with shortness of breath, cough and dysphagia. Radiological examination shows a well demarcated, multilocular cystic mediastinal mass with fat, bone and areas of calcification. On resection, microscopic examination shows cystic cavities lined by stratified squamous keratinized epithelium with adnexal structures underneath. Foci showing undifferentiated mesenchyme, primitive cartilage, neuroectodermal tissue and mature bone are also seen. What is the most likely diagnosis in this case?

  1. Embryonal carcinoma
  2. Immature teratoma
  3. Mature teratoma
  4. Seminoma
  5. Yolk sac tumor
Board review style answer #2
B. Immature teratoma. The radiological findings of the presence of fat, bone and calcification are typical of teratoma. Based on the presence of immature cartilage, mesenchyme and neuroectodermal tissue on microscopy, this represents immature teratoma. Answer C is incorrect because a mature teratoma will not show any such immature components. Answer A is incorrect because embryonal carcinoma does not show derivatives of all 3 germ cell layers; neither do seminoma or yolk sac tumor. Embryonal carcinoma shows uniform population of large polygonal cells with nuclei showing prominent nucleoli, many mitoses and necrosis. Answer D is incorrect because seminoma shows cells divided by incomplete fibrous septae with lymphocytic sprinkling and cells having eosinophilic nucleoli. Answer E is incorrect because yolk sac tumor shows many growth patterns but characteristic endodermal sinus-like formations (also known as Schiller-Duval bodies) can be identified in most cases.

Comment Here

Reference: Germ cell tumors
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