Multidirectional carcinoma of the thymus with neuroendocrine and sarcomatoid components and carcinoid syndrome.

We report a case of metastatic thymic neoplasm occurring in a 62-year-old Caucasian man. The tumor was polymorphic, with intimately admixed carcinoid, sarcomatous and undifferentiated components. Sarcomatous cells were spindle-shaped and immunoreactive for vimentin, actin and desmin. Carcinoid cells reacted for cytokeratin as well as with a panel of general neuroendocrine markers, including chromogranins A and B, synaptophysin, protein gene product (PGP) 9.5, neuron specific enolase (NSE), Leu 7 and Grimelius' silver. The endocrine nature of the latter cells was confirmed by ultrastructural evidence of abundant electron-dense granules 100 to 300 nm in size. Among the various hormones investigated immunohistochemically only the alpha chain of human chorionic gonadotropin (alpha-hCG) was detected in tumor cells. The neoplasm recurred after surgical resection and caused a typical carcinoid syndrome with skin flushing and increased urinary 5-hydroxyindolacetic acid (5-HIAA). The diagnosis of multidirectional thymic carcinoma with two lines of differentiation, of carcinoid and sarcomatoid type, was made.