鼻血管肉腫：一般的な鼻副鼻腔腫瘍との鑑別診断

Angiosarcoma is a rare, highly aggressive vascular malignancy, and sinonasal involvement is exceptionally uncommon. The authors report a 63-year-old man with 6 months of mild epistaxis and progressive nasal obstruction due to a friable mass involving the nasal septum and columella, completely occluding the left nasal cavity. Imaging showed no regional or distant metastases. An initial biopsy elsewhere suggested adenoid carcinoma, but histopathologic re-evaluation of the excised tumor, including immunohistochemistry, revealed angiosarcoma with diffuse nuclear ERG positivity and absence of epithelial markers, confirming its vascular origin. Complete macroscopic resection was achieved through an open approach, and the patient was referred to a multidisciplinary sarcoma board. This case illustrates the diagnostic pitfalls of sinonasal angiosarcoma and emphasizes comprehensive histopathologic assessment and multidisciplinary planning to optimize management of this rare entity.