Malignant transformation of sinonasal inverted papilloma invading the external nose: A case report and literature review.

Sinonasal inverted papilloma (SIP) is a benign neoplasm of the nasal cavity and sinuses, with a certain risk of malignant transformation. The malignant transformation of SIP is uncommon, and the invasion of malignant tumors into the facial skin is even rarer. This report describes the case of a male patient in his 20 s who underwent two endoscopic resections for SIP in the nasal cavity within a 6-year period. Histopathological analysis during the second surgery revealed the malignant transformation of the tumor into squamous cell carcinoma. Despite receiving conventional postoperative radiotherapy, the tumor was not effectively controlled and had invaded the external nasal region. Following a multi-disciplinary team discussion, a treatment plan was established for tumor excision and simultaneous repair using a frontal musculocutaneous flap. The patient received chemotherapy and anti-EGFR therapy following surgery. Tumor recurrence was not observed during the 2-year postoperative follow-up period. The malignant transformation of SIP requires a comprehensive treatment strategy that includes surgical intervention, radiotherapy, chemotherapy, and immunotherapy. Additionally, a thorough assessment and preparation are crucial before flap reconstruction if the tumor invades the external nasal structures and affects appearance.