Solitary fibrous tumor of the periosteum.

We report a solitary fibrous tumor (SFT) of the leg that presented as a pedunculated encapsulated soft tissue mass attached to the periosteum of the posterior tibia. To our knowledge this is the first reported case of an SFT in an extremity. In addition to having the typical gross and microscopic appearance of a usual SFT, this SFT also contained abundant elastic tissue, suggesting an origin from periosteal fibroblasts. This report further extends the anatomic range of the SFT, a neoplasm once thought to be of mesothelial origin but now recognized as a mesenchymal tumor of probable fibroblastic lineage. To date the behavior of the this periosteal SFT has been benign.