title: Osteolipoma of the knee.
abstract: A case of a right knee intra-articular osteolipoma in a 64-year-old man is reported. The patient presented for evaluation of a 1-year history of nontraumatic, mechanically-exacerbated, medial-sided right knee pain. Radiographs demonstrated a partially calcified 3.0 cm mass anterior to the distal medial femur at the suprapatellar fossa. Magnetic resonance imaging examination confirmed a 4.0 × 3.6 cm well-circumscribed mass deep to the medial patellofemoral ligament, with predominantly fat characteristics on T1-weighted and T2-weighted sequences. The mass had irregular ossification superiorly with surrounding heterogeneous enhancement. Histologic examination of an excisional biopsy showed the lesion to be an osteolipoma. Osteolipoma is a rare histologic variant of lipoma with osseous metaplasia, but should be considered in the differential of a fat-containing neoplasm with ossification.
authors.affiliation: Medical Scientist Training Program (MSTP) and Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Tien-Phat V
authors.initials: TV
authors.lastname: Huynh
authors.affiliation: Department of Orthopedic Surgery, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Cara A
authors.initials: CA
authors.lastname: Cipriano
authors.affiliation: Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Ian S
authors.initials: IS
authors.lastname: Hagemann
authors.affiliation: Department of Radiology, Mallinckrodt Institute of Radiology, 510 S Kingshighway Blvd, St. Louis, MO 63110, USA.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Friedman
keywords: Knee joint; Ossifying lipoma; Osteolipoma