Solitary Fibrous Tumor of Kidney

Solitary fibrous tumor (SFT) is a rare spindle cell neoplasm that was initially reported in the pleura, mediastinum, and lungs. Recently, many extrathoracic locations, including kidney and retroperitoneal soft tissues, have been described. The cell of origin is thought to be fibroblast or primitive mesenchymal cell. Most patients are older than 40 years; average age at presentation is 52 years. The tumor may be asymptomatic or cause flank pain, hematuria, and a palpable mass. Some cases of SFT have been associated with hypoglycemia due to abnormal secretion of insulin-like growth factors. The vast majority of cases behave in a benign fashion. About 10%-15% show aggressive behavior resulting in local recurrence or distant metastasis. This photograph of a SFT in a partial nephrectomy specimen shows a well-circumscribed tumor surrounded by a thin rim of renal parenchyma. The tumor has a yellow-tan, homogenous, whorled cut surface. There is no necrosis, cystic change, or hemorrhage. Further discussion of SFT can be found here.