Malignant Myopericytoma: Report of a New Case and Review of the Literature

Abstract

Malignant myopericytoma is a rare entity with only 8 cases reported in the English literature. The authors report a case of a 65-year-old man with a slow-growing 8-cm nodule on the right arm. Marginal excision was performed, and a diagnosis of malignant myopericytoma was made based on histopathologic and immunohistochemical aspects. These tumors are characterized by a proliferation of round-to-spindle cells of myoid appearance in a concentric perivascular arrangement, along with malignant cytological findings. By immunochemistry, the cells were positive for smooth muscle actin and negative for desmin, cytokeratin AE1/AE3, S100 protein, Melan-A, p63, CD99, bcl-2, CD10, and STAT-6. No membranous expression of type IV collagen was observed. These tumors are associated with aggressive biological behavior and most develops metastases.