Immunohistochemical staining of inverted sinonasal papillomas for p53 [115, 175, 178–187] and Ki67 can give useful information concerning the existence of synchronous carcinoma [173, 188] and, in case of high Ki67, a hint toward possible recurrence [136, 177, 189, 190, 190–193]. The gene discussed is MKI67; the disease is carcinoma.