EGFR and inverted papilloma: NC4, as an SNSCC derived from a patient with inverted papilloma (ISP) in medical history, showed a typical EGFR mutation in exon 20 (NM_005228.5: c.2303_2311dup, p.S768_D770dup), whereas the EGFR mutation of NC5 was in exon 6.