Fat-forming solitary fibrous tumor of the kidney: a case report.

BACKGROUND

Solitary fibrous tumor (SFT) arises in many parts of the body, but rarely in the kidney. To the best of our knowledge this is the second report of a fat-forming SFT in the kidney.

CASE

We present a case of a fat-containing SFT at the parihilar region of the kidney in a 64-year-old man complaining of epigastric pain. The tumor was initially diagnosed as angiomyolipoma at hematoxylin and eosin stains. However, by immunohistochemistry the tumor was reclassified as a fat-forming SFT.

CONCLUSION

SFT arises in many sites, but rarely in the kidney. There is also a subset of these tumors that have a variable amount of adipocytic component that should be differentiated from angiomyolipoma. That subset of tumors affects mainly middle-aged adults of either gender and has a wide anatomic distribution. Recurrence is infrequent, and morphologically malignant examples are extremely rare.