Solitary fibrous tumor of the kidney: A case report.

Introduction: Solitary fibrous tumor (SFT) is rare, representing 2% of all soft tissue tumors and is usually described in the thoracic cavity. Only 105 cases of renal SFT have been reported.

Case Presentation: A 55-year-old men with lower urinary tract symptoms, had a routine renal ultrasound which showed a cortical mass of the left kidney measuring 36 × 23 × 39 mm, with peripheral enhancement, and a central fluid collection on CT. On MRI, it was iso-intense to the kidney in T1 and hyper-intense with restricted diffusion in T2 images. The diagnosis of renal cell cancer was likely and an open partial nephrectomy was performed. Microscopic examination showed a mesenchymal neoplasm with long spindle cell and Immunohistochemical staining positive for CD34 and Bcl-2 confirming the diagnosis of SFT. There was no evidence of tumor recurrence or metastasis nine months after discharge.

Discussion: Up to now, only 105 cases of occurring renal SFT have been reported. SFTs are usually asymptomatic when they have a small size, that's why the diagnosis is often delayed. Blood tests do not have any diagnostic value. Imaging features are not specific for the diagnosis of SFT which are diagnosed as renal cell carcinoma and treated as such. Typical immunohistochemical characteristic is a high positivity for CD34. As SFT has a malignant potential, careful follow-up is mandatory,searching for local recurrence or metastasis which was reported in few cases.

Conlusion: SFTs are indolent tumors and are usually diagnosed as renal cell carcinomas preoperatively and the final diagnosis is always based on immunohistochemical study.