Parosteal lipoma of the femur with hyperostosis: case report and literature review.

Lipomas may be defined as benign lesions of mature adipose tissue without evidence of cellular atypia. Lipomas are the most common soft tissue lesions and surprisingly are among the rarest bone neoplasias. Osseous lipomas have been classified according to their site of origin: either within bone (intraosseus) or on its surface (juxtacortical). Surface osseous lipomas are subdivided into parosteal and subparosteal lipomas. Parosteal lipomas often induce a periosteal reaction. The most frequently affected sites are the diaphysis and metaphyseal regions of long bones. The parosteal type is a rare tumor accounting for 0.3% of all lipomas, usually asymptomatic, and affecting mainly adults aged over 40. The most frequent complaints are a tumoral convexity presenting as a visible or palpable mass or a mild-intensity pain. A literature review in the English language MEDLINE database revealed that 12 new cases have been described since the first detailed report of a parosteal lipoma of the femur with hyperostosis by Kenin et al in 1959. The present article describes a rare case of parosteal lipoma located in the femur, with extensive hyperostosis, and reviews this entity in the English language medical literature.