Objective The aim of this study was to investigate the clinical features and prognosis of patients with squamous cell carcinoma (SCC) associated with sinonasal inverted papilloma (IP). Methods The medical records of 95 patients who were diagnosed with IP or SCC associated with IP were retrospectively reviewed. Out of 95 patients, 15 were diagnosed with SCC associated with IP. The clinical characteristics, treatment modalities, and survival outcomes of the patients were analyzed. Results The incidence of SCC associated with IP was 15.8%. Although differential diagnosis between IP and SCC associated with IP is difficult, epistaxis may be the specific symptom in SCC associated with IP cases. The 3-year disease-specific survival rate was higher in cases with T1, 2 and 3 than in cases with T4. There was no significant difference in survival rate between maxillary sinus and other primary sites. On the other hand, there was a significant difference in survival rate between the microscopic SCC with IP cases and the other cases. In addition, the patients with <70 years old better than those with >70 years old with a 3-year disease free survival of 80% versus 0%. Conclusions Some T4 patients were found to have a highly aggressive disease. Therefore, complete surgical resection followed by chemo-radiation therapy is the recommended treatment for patients with T4 disease to control of the primary tumor site.
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