Inflammatory pseudotumor of the kidney.

Renal inflammatory pseudotumor is a very rare benign condition of unknown etiology characterized by proliferative myofibroblasts, fibroblasts, histiocytes, and plasma cells. We report a case of inflammatory pseudotumor of the kidney. A 42-year-old female was admitted with the complaint of right flank pain. Computerized tomography revealed a tumor, 7 cm in diameter, in the upper pole of the right kidney. Right radical nephrectomy was performed under the diagnosis of renal cell carcinoma. Histological examination demonstrated a tumor composed of spindle-shaped fibroblastic cells infiltrated by variable numbers of plasma cells, small lymphocytes and histiocytes. The pathologic diagnosis was renal inflammotory pseudotumor.