Xanthogranulomatous osteomyelitis of ulna mimicking neoplasm

BACKGROUND: Xanthogranulomatous osteomyelitis often presents as a severe chronic inflammation associated with pain, fever, and leukocytosis. It may mimic carcinoma in the involved organs. CASE PRESENTATION: A 50-year-old post-menopausal woman presented with a 2 year history of increasing swelling in the extensor aspect of her right forearm. Plain X-ray revealed an ill-defined expansile osteolytic lesion in the diaphysis of ulna. The gross, microscopic and ultrastructure findings of the curettage specimen was consistent with xanthogranulomatous osteomyelitis. CONCLUSION: This case highlights the rare occurrence of xanthogranulomatous osteomyelitis involving ulna, which can mimic as a primary or secondary bone tumors. A correct diagnosis can only be made on histopathological examination.