Solitary Fibrous Tumor of the Kidney - A Report of Two Cases with Review of Literature -

Solitary fibrous tumor (SF) is a benign mesenchymal neoplasm usually occurring in the pleura. Kidney is one of the rarest sites for SFT. We report here on two cases of renal SET found in 30-year-old and 33-year-old men with review of the literatures. Both cases manifested as well-enhanced solid masses in kidney and radical nephrectomies were done. The tumors consisted of bland-looking spindle cells arranged in short, ill-defined fascicles and storiform pattern with characteristic hemangiopericytoma-like blood vessels. The tumor cells were strongly positive for CD34 and CD99, focally positive for bcl-2, and negative for cytokeratin and human melanoma black-45 on immunohistochemical stainings. Possibility of SET should be considered in the differential diagnosis of a renal mass which consists of benign-looking spindle cells and hemangiopericytomatous blood vessels. Immunohistochemical staining for CD34 is essential to confirm the renal solitary fibrous tumor.