Mediastinal choriocarcinoma

Last revised by Yuranga Weerakkody ◉ on 25 Feb 2022

Mediastinal choriocarcinomas or choriocarcinomas of the mediastinum are malignant non-seminomatous germ cell tumors of the mediastinum consisting of trophoblastic cells.

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Pure choriocarcinomas are rare and account for up to 3% of primary mediastinal germ cell tumors 1. They usually occur in adult men up to the seventh decade 1.

As in for other mediastinal germ cell tumors Klinefelter syndrome is considered as a risk factor 1,2.

The final diagnosis is based on histology as well as immunohistochemistry 1.

The main diagnostic criterion according to the WHO classification is histological evidence of atypical proliferating syncytiotrophoblasts and cytotrophoblasts with dilated vascular sinusoids and frequently areas of hemorrhage and necrosis 1.

A further desirable criterion is the expression of cytokeratins, SALL4, GATA3 and hCG in syncytiotrophoblasts on immunohistochemistry 1.

A large rapidly growing heterogeneous mediastinal mass with pleural and pulmonary invasion in the clinical setting of thyrotoxicosis might be a hint towards the diagnosis.

Clinical signs and symptoms include dyspnea, chest pain, cough and hemoptysis as well as superior vena cava syndrome, syncope, headache and cardiac tamponade 1,2. Some patients might present with gynecomastia or thyrotoxicosis 1,3.

Mediastinal choriocarcinomas might cause the following complications 1-3:

  • superior vena cava obstruction
  • infiltration of adjacent structures
  • pericardial effusion and/or cardiac tamponade
  • pleural effusion
  • lymph node and distant metastases
  • thyrotoxicosis

Mediastinal choriocarcinomas are malignant non-seminomatous germ cell tumors primarily composed of syncytiotrophoblasts and cytotrophoblasts. They usually occur in combination with other histologic tumor types 1,2.

Mediastinal choriocarcinomas apparently host an isochromosome 12p. A hypothesis is an aberrant midline migration of primordial germ cells 1.

Primary mediastinal choriocarcinomas can be found in the anterior mediastinum and posterior mediastinum 1.

Mediastinal choriocarcinomas are often large at the time of diagnosis with a soft and fragile consistency, extensive areas of hemorrhage and focal necrotic areas 1,2.

Microscopically mediastinal choriocarcinomas are characterized by the following features 1-4:

  • intermingled syncytiotrophoblasts and cytotrophoblasts
    • syncytiotrophoblasts: large pleomorphic multinucleated cells with hyperchromatic nuclei
    • cytotrophoblasts: medium-sized mononucleated cells with basophilic cytoplasm and eccentric nuclei
  • common atypical mitosis and cellular atypia
  • dilated vascular sinusoids
  • extensive hemorrhage and necrosis

Immunohistochemistry stains are usually positive for SALL4, GATA3 and cytokeratins. Syncytiotrophoblasts express glypican-3 hCG and ɑ-inhibin. OCT4, AFP, CEA, PLAP, CD30 and vimentin are usually negative 1.

Descriptions of imaging features of mediastinal choriocarcinomas are scarce. They are described as heterogeneous and characterized by hemorrhagic and necrotic areas 2,3.

Chest x-rays might show widening of the anterior mediastinum.

On chest CT, mediastinal choriocarcinomas have been described as well-defined and heterogeneous with areas of hemorrhage and/or necrosis 3. Pleural or pericardial effusions might be present.

The radiological report should include a description of the following:

  • location and extent of the tumor
  • relation to the heart and great vessels
  • associated complications (e.g. superior vena cava obstruction, pleural or pericardial effusion)
  • nodal disease
  • distant metastases

Management includes cisplatin-based chemotherapy and possibly surgery. Prognosis is poor with a short overall survival time of months 1, 3-5.

Condition or tumors that might mimic the appearance of tumors include 1:

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