A rare pericytic tumor of the kidney: The first case in Korea.

Introduction: A pericytic tumor is a group of mesenchymal neoplasm found in superficial tissues and only rarely described in viscera. The family of pericytic tumors includes glomus tumors and variants, myopericytoma including myofibroma, and angioleiomyoma etc. The renal pericytic tumor is extremely rare, and only few comprehensive discussions about this entity have been done.

Presentation Of Case: A 58-year-old man was transferred to our institute with suspicions of renal cell carcinoma. The kidney dynamic computed tomography scan showed a 3 cm sized solid mass in the upper pole of the right kidney. Laparoscopic radical nephrectomy was performed due to the deep-seated mass. Pathological result confirmed that the kidney mass was renal pericytic tumor.

Discussion: Although general biological behavior of published renal pericytic tumors is likely to be benign, the clinicopathologic experiences are very limited. Therefore, we should evaluate the malignant potential of the entity according to the parameters proposed for soft tissue tumors, including tumor location, tumor size, growth pattern, cellularity, cytological atypia, and mitotic figures with atypical forms. The current case shows several worrisome features, including an extremely rare tumor location, partially infiltrative growth, and a mildly increased proliferating index, which resulted in it being classified as an uncertain malignant potential.

Conclusion: We described the first case of renal pericytic tumor, addressing uncertain malignant potential, in a Korean male, which would be a distinct mesenchymal neoplasm differentiating from other groups of perivascular tumor families based on histological and immunohistochemical features.