Clinicopathologic and genetic characterization of traditional serrated adenomas of the colon

Traditional serrated adenomas (TSAs) are a type of colorectal polyp with neoplastic potential. Immunohistochemical analysis and sequencing were performed on 24 TSAs from 23 patients to characterize the molecular genetics of TSAs. Abnormal Ki-67 and p53 labeling were observed in 7 (29%) of 24 and 6 (25%) of 24 TSAs, respectively; both types were significantly associated with the presence of conventional epithelial dysplasia (P = .0005 and P = .0001, respectively). Activating KRAS mutation was identified in 11 TSAs (46%) and was mutually exclusive with activating BRAF mutations, which were seen in 7 TSAs (29%). Abnormal p53 nuclear labeling in a TSA was significantly associated with BRAF mutation status (P = .04), whereas no relationship was found for β-catenin labeling patterns. The overall morphologic features of TSA do not correlate with the genetic status of the KRAS and BRAF genes. However, conventional epithelial dysplasia and abnormal p53 labeling in a TSA are seen more often in the setting of BRAF mutation.