Mediastinal germ cell tumor associated with histiocytic sarcoma of spleen: case report of an unusual association.

We present an unusual association of mediastinal germ cell tumor containing seminoma and angiosarcoma components and splenic histiocytic sarcoma. A 15-year-old boy presented with chest pain. Histopathologically, an anterior mediastinal mass contained typical seminoma, immature teratoma, embryonal carcinoma, angiosarcoma, yolk sac tumor, and polyembryoma. An abdominal ultrasonogram revealed a huge splenomegaly with multiple ill-defined low echogenic nodules, 1 month after the second cycle of chemotherapy. Histopathologically, large, round-to-oval tumor cells with abundant eosinophilic cytoplasm often contained eccentrically placed nuclei with vesicular chromatin and an irregular nuclear membrane. The tumor cells were immunoreactive for CD68, CD31, and CD4. The cytogenetic results showed deletion of the long arm of chromosome 5 and trisomy 8. This lesion might have been on the pathway of multistep tumorigenesis toward a final leukemia.