A Huge Intraosseous Hemangioma in the Maxillary Sinus Misdiagnosed as Osteosarcoma: A Case Report.

Intraosseous hemangiomas are rare benign vascular tumors that account for less than 1% of all bone tumors and are exceptionally uncommon in the sinonasal region. Their aggressive-appearing radiological features may mimic those of malignant bone tumors, creating diagnostic challenges. An 18-year-old man presented with right-sided nasal obstruction and epistaxis. Imaging revealed a large destructive mass in the right maxillary sinus that was suspicious for malignancy, including osteosarcoma. Endoscopic biopsy showed nonspecific benign osseous features that were discordant with the radiological findings. For this reason, endoscopic medial maxillectomy was performed. Histopathological examination with CD31 and CD34 immunostaining confirmed intraosseous venous hemangioma. Intraosseous hemangioma should be considered in the differential diagnosis of aggressive-appearing sinonasal masses, especially when imaging and biopsy findings are discordant, as its recognition may help prevent unnecessarily aggressive treatment.