Renal myopericytoma with nephrotic syndrome: report of a case and review of literature

Objectives: With its other counterparts like myofibroma, angioleiomyoma and glomus tumor, myopericytoma is a benign subtype of pericytic tumors and only 4 cases are involved in kidney in literature. Methods: Standard pathological examination (including macroscopical and histopathological analysis) and immunohistochemistry of sections were performed. Results: We described a 19-year-old woman, who discovered a renal mass in her 24th gestational week with nephrotic syndrome. Radical right nephrectomy was done after careful examination and induced labor. Microscopically, the tumor was composed of numerous slit-like, thin-walled vessels, surrounded by spindle-shape or polygonal neoplastic cells in a strip-like arrangement. Immunohistochemical staining revealed positive expression in actin, CD10 and bcl-2, negative in Vimentin, Melan-A, HMB-45, CD34, pan-cytokeratin, HMWcytokeratin, Desmin, E-cadherin, et al.; Ki-67 index showed a low proliferative rate, thus the diagnosis of myopericytoma (MPC) was established. This is an uncommon finding of MPC in morphology. After a follow-up of 8 months, the patient showed no evidence of tumor recurrence or metastasis. We also review other reports of renal myopericytoma. Conclusions: Our case is the fifth case of renal myopericytoma according to the reported literature. At the same time, our case has uncommon pathological morphology.