A biopsy was performed, and the histopathologic diagnosis was malignant fibrohistiocytoma. The lesion was resected with reconstruction of the tibia using a fibular graft, without recurrence at 5-year followup. SLE and corticosteroids are well-established risk factors for osteonecrosis. Irrespective of their cause, areas of osteonecrosis involving metaphysis and diaphysis of long bones (infarcts) can be associated with sarcomas over time, unlike those affecting subarticular regions and epiphysis (avascular necrosis) (1-3). Histologic types include malignant fibrohistiocytoma (the most common), osteosarcoma, fibrosarcoma, angiosarcoma, and epithelioid hemangioendothelioma (1-3). Nearly 75% of patients have multiple foci of infarcts, men are affected twice as frequently as women, and the distal femur and proximal tibia are the typical sites of this rare complication (2). Reactive tissue at the periphery of the infarcts has been suggested as the source of these sarcomas (1,2). The appearance of pain with an aggressive lesion seen by radiography at a site of an evident infarct should raise suspicion of infarct-associated bone sarcoma (1,2), which usually has a poor prognosis (3).