Frequent Recurrence of Sinonasal Inverted Papilloma With Carcinoma In Situ in a Multifocal Attachment Pattern: A Case Report and Review of the Literature.

Sinonasal inverted papilloma (SIP) is a benign tumor originating from the nasal cavity and paranasal sinuses. Sinonasal inverted papilloma is characterized by local infiltration, high recurrence, and malignant transformation, and its associated dysplasia ranges from mild, moderate, severe, carcinoma in situ (CIS) to invasive squamous cell carcinoma. Sinonasal inverted papilloma with carcinoma in situ (IPwCIS) is the highest degree of dysplasia, which is a stage of malignant transformation of IP. Surgical excision and proper adjuvant therapy can help reduce recurrence rates and suppress further deterioration. In this study, we present a patient with IPwCIS who developed 3 recurrences with a multifocal attachment pattern in less than 18 months. We report the clinical manifestations, development, and treatment process in detail. We also performed a literature review to analyze the characteristics of the disease. Despite comprehensive treatment methods, tumor recurrence and further deterioration of IPwCIS persist.