Discussion
Our study indicates that in patients with SPS, the ratio of sCRCs:aCRCs on average is 50:50. This elevated sCRC:aCRC ratio in patients with SPS, when compared with non-SPS patients, correlates well with the differences in the ratios of the numbers of sessile serrated lesions and conventional adenomas in patients with SPS and non-SPS patients, respectively.
Methods
We collected endoscopy and pathology data on CRCs and polyps of patients with SPS under treatment in our center. Our primary end point was the proportion of BRAFV600E mutated CRCs, indicating serrated pathway CRCs (sCRCs). CRCs lacking BRAFV600E most likely inferred a classical adenoma-carcinoma origin (aCRCs). We assessed patient, polyp, and CRC characteristics and stratified for BRAFV600E mutation status.
Results
Thirty-five patients with SPS harbored a total of 43 CRCs. Twenty-one CRCs (48.8%) carried a BRAFV600E mutation, 10 of which lacked MLH1 staining and 17 (81%) were located in the proximal colon. Twenty-two CRCs (51.1%) did not carry a BRAFV600E mutation and were MLH1 proficient. Of these 22 putatively aCRCs, 17 (77.3%) were located distally and one-third (36.4%) harbored a pathogenic KRAS or NRAS mutation. In patients with BRAFwt -CRCs, a higher ratio of the median number of conventional adenomas versus serrated polyps was found (4 vs 13) than patients with BRAFV600E -CRCs (1 vs 14).