BENIGN FIBROMATOUS TUMOR (FIBROMA) OF THE KIDNEY - A CASE-REPORT

Benign fibromatous tumor (fibroma) of the urogenital tract is a distin ctive pathologic entity occurring in the testis, paratesticular struct ures and renal peripelvis. We report a well-circumscribed tumor replac ing the cortex and the medulla of more than half of the upper kidney, radiographically thought to be renal cell carcinoma. Histologically, t he tumor was characterized by a variable cellularity and was composed of bland spindle-shaped cells loosely dispersed in a fibromyxoid to de nsely fibrous stroma in which calcifications and chronic inflammation were not observed. Immunocytochemistry showed that cells were positive for vimentin and, only focally, stained positive for desmin and alpha -smooth muscle actin. Differential diagnosis included a wide spectrum of benign and malignant spindle cell tumors. The clinicopathologic fea tures were consistent with benign fibromatous tumor (fibroma) of the k idney. To our knowledge, this is the first case of benign fibromatous tumor (fibroma) of the kidney reported in the English literature.