A case report of xanthogranulomatous osteomyelitis of the distal ulna mimicking a malignant neoplasm

PATIENT Male, 59 FINAL DIAGNOSIS: Xanthogranulomatous osteomyelitis Symptoms: Painful swelling in the wrist Medication: Drug history of antifulgal agents Clinical Procedure: Excisional biopsy Specialty: Radiology. OBJECTIVE Rare disease. BACKGROUND Xanthogranulomatous inflammation is a chronic inflammatory disease in which bone involvement is extremely rare. Bone involvement of xanthogranulomatous inflammation, termed xanthogranulomatous osteomyelitis (XO), often presents as a mass-like lesion extending to adjacent structures, which can mimic infiltrative carcinoma. CASE REPORT We present a case of XO in the ulna, which mimicked a neoplasm. A 59-year-old man presented with a 2-month history of painful swelling in the right wrist. Plain radiography and CT showed an osteolytic lesion at the distal ulna. MRI revealed a soft-tissue mass with lobulated margins and contrast enhancement. Intense uptake in bone scan and PET suggested malignancy. An excisional biopsy from the representative area resulted in a pathology diagnosis of XO. CONCLUSIONS Gross and radiologic manifestations of XO can mimic neoplasm. XO generally has benign prognosis, contrary to malignant bone tumor. Therefore, biopsy and histopathological confirmation are necessary for proper management.