Solitary Fibrous Tumor of the Thigh: A Patient Report

We report a rare case of solitary fibrous tumor (SFT) within the thigh muscle. A 37-year-old woman noticed a painless mass in her left thigh, which had gradually enlarged. Computed tomography (CT) showed an intramuscular tumor and enhanced CT showed strong enhancement within the lesion. Magnetic resonance imaging revealed that the tumor measured 13.1 × 7.3 × 2.3 cm and was located within the sartorius muscle, with a clearly defined margin. Malignancy was suspected and the tumor was surgically resected. The tumor was characterized by a well-circumscribed lesion, and was composed of bland or short spindle cells, which were patternless, with scattered thick collagen bundles, and variably gaping thin- or hyalin-walled blood vessels. Immunohistochemically, the tumor cells were positive for vimentin, CD34, CD99 and focally, bcl-2. The tumor was subsequently diagnosed as an extrapleural SFT, which is classified into an intermediated (rarely metastasizing) category. Extrapleural SFT should be considered in the evaluation of soft tissue tumors in the extremities, although it may be rare.