[Clinicopathologic features of solitary fibrous tumor in urogenital system]

To study the clinicopathologic features and differential diagnosis of solitary fibrous tumor (SFT) in the urogenital system.

The clinical data and pathologic characteristics of eight cases of SFT in the urogenital system were analyzed, and the relevant literature was reviewed.

The cohort included six male and two female patients, with age of onset ranging from 25 to 80 years. Five occurred in the kidney (three in the right kidney), one case each occurred in the bladder, the prostate and the spermatic cord. Most patients showed no obvious clinical symptoms or only had low back pain and swelling. The diameter of the tumor was ranged from 2.5 to 11.8 cm (median 5.2 cm). Microscopy showed at low magnification, the tumor cells were spindle-shaped and arranged in bundles or helicoid pattern. The regional mesenchymal fibroblasts showed hyperplasia, with obvious collagenization and formed hemangiopericytoma-like structure. One case showed increased mitotic figures (>5 cells/10 HPF) and focal necrosis. By immunohistochemistry, the tumor cells were positive for CD34 and STAT6 in all eight cases, CD99 and vimentin in six cases, bcl-2 in four cases and SMA in one case. All seven cases with follow-up did not show any tumor recurrence or metastasis.

SFT is rare in the urogenital system and most patients show good prognosis. SFT expresses CD34 and STAT6 and needs to be distinguished from other spindle cell tumors.