Background: The mechanism underlying the malignant transformation of inverted papilloma (IP) has not yet been elucidated. Methods: To clarify the genes responsible for the malignant transformation, we analyzed 10 cases of IP, 8 of IP with dysplasia, and 11 of squamous cell carcinoma (SCC) by targeted amplicon sequencing. Results: The number of mutant genes increased in the order of IP < dysplasia < SCC. Significant differences were observed in the mutation rates of three genes (KRAS, APC and STK11) in particular. TP53 was altered frequently in each group and might be involved in malignant transformation based on to the site of the mutation. A comparison of the genetic variants by region of IP tissue among patients with IP alone, and those with dysplasia or SCC revealed significant differences in the mutation rate of the KRAS gene. Conclusion: Identification of genetic mutations in KRAS is effective for predicting the malignant transformation of IP.
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