Choriocarcinoma is a highly malignant neoplasm composed of syncytiotrophoblasts, cytotrophoblasts, and variably intermediate trophoblast cells. Mediastinal choriocarcinomas are morphologically indistinguishable from their gonadal or uterine counterparts.

Pure mediastinal choriocarcinomas are exceedingly rare and virtually nonexistent in children.^{1,2,3,4,5,6,7,8,9,10} The tumor occurs almost exclusively in young males. Only 2.5% to 5% of mediastinal GCTs are pure choriocarcinoma.^{11,12,13,14,15}

The patients’ ages range from 17 to 63 (most commonly the third decade of life).^2,7,9 At diagnosis, mediastinal choriocarcinomas are mostly large anterior mediastinal masses. The patients present with symptoms due to the mediastinal mass, such as chest pain, dyspnea, cough, and superior vena cava syndrome. Patients may show gynecomastia due to elevated beta-hCG levels.^2,7,9 Mediastinal choriocarcinomas are highly aggressive neoplasms with early hematogenous dissemination. Metastatic disease to the lungs, liver, kidney, spleen, brain, heart, adrenals, and bone has been observed.^9,10