Abstract

Background: Parosteal lipoma is a rare benign tumor of mature adipose tissue located on the surface of bone firmly adherent to the periosteum. It is typically associated with reactive changes in the underlying bone in the form of cortical thickening, erosions, or bowing which may complicate the clinical picture. In this report, we present a case of parosteal lipoma of the femur associated with exuberant bony changes and clinical concern of an impending fracture.
Case presentation: A 33-year-old female presented with right thigh pain and limping. Multimodality imaging revealed a juxtacortical fat-capped exostosis-like lesion located against the upper meta- diaphysis of the femur accompanied by cortical bone protuberances, focal cortical erosion, and an intramedullary lytic component. A needle core biopsy was performed due to concerns regarding the bony reaction but failed to yield diagnostic material. The patient was considered at increased risk of developing a pathological fracture due to the significant functional pain and the radiological findings and underwent an open excisional biopsy and prophylactic fixation of the impending fracture. Finally, pathological evaluation confirmed the diagnosis of parosteal lipoma and the reactive nature of the bony changes.
Conclusion: Parosteal lipoma is a rare benign lesion occurring on the surface of bone which may resemble exostosis or other more aggressive parosteal tumors. Although histopathological evaluation is often regarded as a gold standard, radiology-pathology correlation is mandatory for establishing the correct diagnosis especially on small biopsy samples. Accurate preoperative recognition of parosteal lipoma and distinction from other juxtacortical bone tumors will aid in appropriate surgical planning.