Intraosseous lipoma. A clinical, radiologic, and pathologic study of 5 cases.

Intraosseous lipoma is an uncommon tumor of bone with indistinct radiologic features that makes it diagnostically challenging to radiologists and pathologists. There is a need to familiarize these physicians with the radiographic and pathologic features of this lesion for the correct diagnosis. We described the radiologic and pathologic features of intraosseous lipoma in 5 women. In 4 patients, the tumors occurred in long bones, whereas in the fifth patient, the skull was involved. Patients' age ranged from 50 to 63 years. Plain radiographs of the long bones revealed well-circumscribed benign-appearing osteolytic lesions with sclerotic margins, whereas in the skull, a poorly defined lytic aggressive-looking lesion was observed. In the long bones, the lesions showed remodeling of the affected bone with matrix calcification, simulating bone infarcts. Microscopically, mature adipose tissue with fat necrosis, absence of hematopoietic elements, and dystrophic calcification corresponding to the calcified matrix seen on the plain radiographs were seen. The osteolytic skull lesion had large caliber thin-walled vasculature with occasional fibrin thrombi mimicking intramuscular hemangiomas of soft tissue. On plain radiographs, an intraosseous lipoma is usually seen as a rather benign-appearing osteolytic bone lesion with well-defined margins and a heavily calcified/ossified dense matrix. Plain radiographs alone cannot establish the diagnosis of intraosseous lipoma as it mimics several other benign and malignant bone lesions. Intraosseous lipoma often contains calcified necrotic fat with little mature adipose tissue and characteristically induces expansion/remodeling of the affected bone.