Smoking and malignancy in sinonasal inverted papilloma.

OBJECTIVES/HYPOTHESIS The authors investigated clinical features of squamous cell carcinomas (SCC) arising in sinonasal inverted papillomas (IP) and risk factors responsible for their malignant transformation. STUDY DESIGN Retrospective analysis. METHODS In total, 162 patients diagnosed with sinonasal IP and treated between 1998 and 2009 at Pusan National University Hospital were enrolled. Their demographic data, information about previous surgery, smoking history, treatment modalities, follow-up duration, recurrence, and presence of malignancy were reviewed retrospectively. RESULTS Seventeen patients (10.5%) were diagnosed with SCC arising in sinonasal IPs. Among them, nine (9/162, 5.6%; 9/17, 52.9%) were diagnosed with synchronous malignancies and three (3/162, 1.8%; 3/17, 17.6%) were diagnosed with metachronous malignancies. In five cases (5/162, 3.1%; 5/17, 29.4%), we could not determine whether their malignancies were synchronous or metachronous. Among 53 smokers, 14 (26.4%) had malignant transformation, while only three (2.8%) in 109 nonsmokers had malignant transformation (Odds ratio = 12.7; P < .001). The mean follow-up in the 17 patients with malignancy was 47.0 months. Three patients did not receive surgical treatment and died of progression of SCC. Among the other 14 patients who underwent curative surgeries, four (28.6%) had recurrences, and their mean period to cancer recurrence was 6.3 months. Two of them died of progression of the cancer. Mean survival of the five patients who died was 14.0 months. They all belonged to T4 stage. CONCLUSIONS Smoking history is associated with malignant transformation of sinonasal IP. It suggests that close follow-up be required in smokers with sinonasal IP in order not to overlook the malignant transformation. LEVEL OF EVIDENCE 2b.