Renal myopericytoma: a clinicopathologic study of six cases and review of the literature.

To evaluate the morphologic features, immunohistochemical profiles, and biological behavior of renal myopericytoma. Six cases of renal myopericytoma are retrospectively retrieved and analyzed by H&E and immunohistochemical staining. Clinically, patient's age ranged from 33 to 70 years (median, 56 years). Male to female ratio was 5:1. Five of the six patients were asymptomatic of the urinary tract, the remained one presented with abdomen pain. Grossly, all six tumors were solitary masses with sizes ranging from 1.8 to 7.3 cm of maximum diameter (mean, 4.4 cm). Five tumors were described as well-circumscribed, and 1 case was showed as ill-defined. Histologically, in all cases, numerous thin-walled vessels and a perivascular arrangement of ovoid, spindled or round myoid tumor cells were seen. However, a broad morphologic spectrum ranging from fibroma-like (3 cases), glomangiopericytoma-like (3 cases), angioleiomyoma-like (2 cases), glomoid- like (2 cases), and myofibroma-like (2 cases) components were observed. In addition, 1 neoplasm with immature cellular features and another infiltrating myopericytoma were found. A coexisting papillary adenoma was detected in 1 case. Nuclear atypia was seen in 2 cases. Immunohistochemically, SMA, caldesmon, and MSA were positive in all 6 cases, whereas CD34 and desmin was partial positive in 1 case, respectively. Ki67 index was aproximately 5% in 1 case but less than 2% in the others. All patients are free of disease by follow-up ranging from 14 to 66 months (mean, 38.7 months).