Renal myopericytoma: A case report with a literature review.

Myopericytoma is a rare neoplasm that generally arises from the skin and superficial soft tissues of distal extremities, and is particularly rare in the visceral organs. The current report presents a case of giant myopericytoma showing kidney involvement, which is extremely rare. A 39-year-old male presented to the Department of Urology with a 2-month history of a painless and palpable mass in the region of the left abdomen. Unenhanced computed tomography revealed a 9×10×18-cm(3) mass that was heterogeneous with central lower density. The patient underwent radical nephrectomy, including lymphadenectomy, without adjuvant therapy. The tumor was composed of spindle-shaped myoid cells with a concentric arrangement and showed immunoreactivity for smooth muscle actin and cluster of differentiation (CD)10, and had a Ki-67 index of <1%; however, staining was negative for CD34, desmin, S-100 protein, cytokeratin, human melanoma black (HMB)-45, B-cell lymphoma (Bcl)-2 and CD99. Routine follow-up revealed no local or distant metastatic signs of reccurrence for 20 months. The present report shows that renal myopericytoma may be a benign tumor, and surgical excision without adjuvant therapy may be the only potentially curative treatment approach.