Xanthogranulomatous Osteomyelitis of Proximal Femur Masquerading as Benign Bone Tumor.

We describe a case of xanthogranulomatous osteomyelitis (XO) of the proximal femur in a 65-year-old woman who presented with pain of 6 months' duration in the right hip. Plain radiographs showed a lytic well-defined lesion in the right peritrochanteric region suggestive of a benign neoplastic etiology. The gross and histopathologic examination of the curettage specimen was consistent with XO. Xanthogranulomatous osteomyelitis is a rare chronic inflammatory process that is characterized by the presence of a large number of lipid-containing macrophages with an admixture of lymphocytes, plasma cells, and neutrophils. Gross and radiologic examination of this entity can mimic malignancy, and differentiation should be confirmed by histopathologic evaluation. To the best of our knowledge, XO of the femur has not been reported in the English-language literature. The rarity of this condition and its resemblance to bone tumors form the basis of this case report.