Osteoma infiltrated by schwannoma in sinonasal region: radiologically masquerading as a malign tumor

Neoplasms in sinonasal cavity are dominated by epithelial type. Sinonasal osteomas are common, benign, slow-growing, often asymptomatic neoplasms occurring mainly in the frontal and ethmoid sinuses. Peripheral nevre sheath tumors are soft tissue neoplasms rarely encountered in the sinonasal region. Schwannoma is a benign peripheral nevre sheath tumor. Here, we presented co-occurence of osteoma and schwannoma. So far, osteoma infiltrated by schwannoma in sinonasal region is not reported in English literature. Additionally it was masquerading as malignant tumor radiologically. The pathologist should be aware of a second soft-tissue tumor that may accompanied the radiologically suspicious malignant bone lesions.