The American journal of surgical pathology
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Am. J. Surg. Pathol. · Sep 2017
WNT Pathway Gene Mutations Are Associated With the Presence of Dysplasia in Colorectal Sessile Serrated Adenoma/Polyps.
Sessile serrated adenoma/polyps (SSA/Ps) are believed to be the major precursor of serrated pathway-derived colorectal carcinomas. To better characterize the process of progression from SSA/Ps to carcinomas, we analyzed 46 SSA/Ps with dysplasia and 45 SSA/Ps without dysplasia using targeted next-generation sequencing and immunohistochemistry. Among the WNT pathway genes analyzed, protein-truncating mutations of RNF43, APC, and ZNRF3 were identified in 23 (50%), 4 (9%), and 3 (7%) SSA/Ps with dysplasia, respectively. ⋯ The majority of MLH1-deficient SSA/Ps with dysplasia had RNF43 mutations (86%), most of which were frameshift mutations involving mononucleotide repeats. In contrast, MLH1-retained lesions had less frequent RNF43 mutations with no hot spots (34%), and 4 had APC mutations (13%). These results suggest that WNT pathway gene mutations are involved in the development of dysplasia in SSA/Ps and that MLH1-deficient and MLH1-retained SSA/Ps with dysplasia exhibit distinct mutation profiles of WNT pathway genes.