Ossifying chondroid lipoma.

Chondroid lipoma is a rare variant of lipoma that pathologically can mimic liposarcoma or possibly other sarcomas. Variants of lipoma, including chondroid lipoma, may demonstrate radiological evidence of fat within the tumor, but often display heterogeneous features on imaging studies, making a clinical diagnosis difficult. A large collective experience with the imaging characteristics of chondroid lipoma is lacking due to the rarity of this tumor. We present a case of chondroid lipoma of the upper thigh in a 37-year-old woman who had regions of metaplastic bone formation within the tumor. Radiologically, the tumor presented as a large soft tissue mass with calcification and ossification. Although metaplastic bone formation in conventional lipoma is well described, it has been rarely reported to occur in chondroid lipoma and has not been pathologically documented or illustrated. The imaging findings and histopathology of this unusual tumor are presented, along with a review of the literature.