We report a mediastinal
germ cell tumor (GCT) that exhibited a discrepancy between the time course of serum
human chorionic gonadotropin (hCG) levels and clinical consequences. An otherwise healthy man, aged 34 years, was diagnosed with a nonseminomatous GCT, most likely
embryonal carcinoma (EC), based on a mediastinal
tumor biopsy. Standard
chemotherapy resulted in an optimal decrease in serum hCG levels. However, multiple lesions in the liver continued to enlarge, which led to his death. Autopsy revealed few viable
tumor cells in the liver, with the great majority of the
tumor cells appearing to have undergone
necrosis, suggesting that they responded to the
chemotherapy. The
residual tumor cells in the mediastinum and the liver were similar to syncytiotrophoblast cells, suggesting a cho-riocarcinoma (CC). On immunohistochemical analysis, the mediastinal
tumor cells in the diagnostic biopsy specimen expressed both CD30 and hCG, whereas residual mediastinal and hepatic
tumor cells in the autopsy specimen after
chemotherapy also expressed hCG, but not CD30. These findings suggested that the patient suffered from a primary mixed GCT consisting of an EC and a CC. Both pre- and postchemotherapy
tumors strongly expressed
matrix metalloproteinase-2, supporting the aggressive and invasive features of the
tumor phenotype. We speculate that the extremely invasive
tumor destroyed normal liver structure, whereas
chemotherapy and central
necrosis reduced the number of viable cells themselves, causing a discordant decrease in serum hCG levels.