Pheochromocytoma combined with malignant schwannoma: unusual neoplasm of the adrenal medulla.

A 38-year-old woman was operated on to remove a large tumor that replaced the left adrenal gland. The tumor was encapsulated and showed small areas typical of pheochromocytoma, and spindle cell or undifferentiated round cell sarcoma in most areas. Metastases of primitive round cell appearance were operated from the abdominal cavity and abdominal wall shortly after the initial surgery. Eighteen months after the first operation, the patient was alive with metastases in liver and retroperitoneal space. The pheochromocytomalike component showed a typical ultrastructural and immunohistochemical profile of pheochromocytoma and was positive for neurofilaments, synaptophysin, neuron-specific enolase, and S-100 protein in the sustentacular cells. The sarcomatous areas showed fibroblastoid spindle cells that were often surrounded by a basal lamina. Immunohistochemistry revealed S-100 protein positivity in many spindle cells, but markers of pheochromocytoma or epithelial differentiation were absent. The metastases lacked all markers except for vimentin, and the cells were undifferentiated by electron microscopy. These findings suggest that the neoplasm was a compound tumor with a typical pheochromocytoma component and a sarcoma resembling a malignant schwannoma. Neoplastic proliferation of the S-100 protein-positive Schwann-cell-like sustentacular cells of the pheochromocytoma would be an explanation for the genesis of this sarcoma associated with pheochromocytoma.