Benign Fibrous Histiocytoma of the Renal Capsule

The first case of benign fibrous histiocytoma of the renal capsule is reported in a male aged 44 years. The tumor had its point of origin in the renal capsule. Histologically, the tumor was composed of intersecting fascicles of fibro‐blastic cells forming a loose crisscross or “storiform” pattern. Electron microscopic studies of tumor cells revealed intermediate filaments and membrane‐bound collagen fibers which continued to extracellular collagen bundles. This deep‐seated fibrous histiocytoma had a more prominent storiform pattern and fewer secondary elements such as xanthoma cells than cutaneous ones. Acta Pathol Jpn 42: 217 220, 1992.