KRAS mutation occurred more frequently (26.5%) than BRAF mutation (4.8%) in adenomas (P < 0.001) and particularly in adenomas with villous architecture (50%).
BRAF gene mutations in the colorectum have been associated with serrated adenomas and less frequently with hyperplastic polyps, villous adenomas, tubular adenomas, and carcinomas.
Our data suggest that BRAF mutations are, to some extent, biologically similar to RAS mutations in colorectal cancer because both occur at approximately the same stage of the adenoma-carcinoma sequence, both are associated with villous morphology, and both are less common in adenomas from FAP cases.
We investigated 194 serrated lesions of the colon, comprising 42 sessile serrated adenomas/polyps, 16 traditional serrated adenomas, 136 hyperplastic polyps and 20 tubular/tubulovillous adenomas (conventional adenomas) with the novel BRAFV600E mutation-specific antibody VE1.
The presence of BRAF mutations in these adenomatous precursors suggests that they represent sessile serrated adenomas with complete cytologic dysplasia.
TSAs were classified into two phenotypes according to their molecular characteristics: microvesicular serrated subtypes with BRAF mutations (SA-1 and -2 lesions) and subtypes containing tubulo-serrated/conventional adenoma with K/NRAS mutations (SA-3 and -4 lesions).
Synchronous colorectal cancer (HR 1.82; 95% CI 1.15-2.87; P=0.01), synchronous advanced adenoma (HR 1.81; 95% CI 1.27-2.58; P=0.001), and BRAF(c.1799T>A) mutation (HR 2.16; 95% CI 1.25-3.73; P=0.01) were stage-independent predictors of death from MSS CRC.
We evaluated miR-31 expression, BRAF mutation and epigenetic features including CIMP status in 381 serrated lesions and 222 non-serrated adenomas and examined associations between them and tumor location (rectum; sigmoid, descending, transverse and ascending colon and cecum).
Systematic review and meta-analysis was performed by searching electronic databases from January 2011 to January 2019 for studies assessing the association of BRAF-V600E mutation with clinical or pathological features of serrated adenomas.
Hierarchical clustering isolated three relevant clusters: (i) cluster of microsatellite stable mucinous adenocarcinomas (54%) with KRAS mutation, and frequent MGMT changes, more frequently located in the left colon, often associated with contiguous precursor adenoma; (ii) cluster of BRAF-mutated mucinous adenocarcinomas (28%) with either microsatellite instability-high or microsatellite stable status, occurring in elderly female patients, nearly all located in the right colon, having the signature of serrated pathway of carcinomas; and (iii) a heterogeneous cluster of microsatellite instability-high mucinous carcinomas (18%), including inherited colorectal carcinomas, displaying a high-grade histological pattern.
Our results demonstrate that KRAS are more prevalent than BRAF mutations in SAC (42.7% vs. 25.8%; p = 0.011) being the KRAS-mutated cases even more abundant in SAC displaying adjacent serrated adenomas (51%).
Based on the current knowledge, the sessile serrated adenoma/polyp may be the major precursor of MLH1-methylated CIMP-H CRCs, whereas MLH1-unmethylated CIMP-H CRCs may develop predominantly from KRAS-mutated traditional serrated adenomas and less commonly from BRAF-mutated traditional serrated adenomas and/or sessile serrated adenomas/polyps.
We analyzed immunoreactivity of these proteins, methylation of PTCH and EphB2, and mutation of BRAF and Kras in sessile SAs (SSAs; n = 32), traditional SAs (n = 28), hyperplastic polyps (HPs; n = 24), and conventional adenomas (ADs; n = 21).
In one out of four serrated polyposis families, we identified a germline RNF43 mutation that displayed autosomal dominant cosegregation with the serrated polyposis phenotype, along with second-hit inactivation through loss of heterozygosity or somatic mutations in all serrated polyps (16), adenomas (5) and cancer (1) examined, as well as coincidental BRAF mutation in 62.5% of the serrated polyps.
Mixed effects models revealed that mutations in APC, BRAF and KRAS occur at the transition from normal to adenoma stages whilst the hypermethylation of the Wnt antagonists continued to accumulate during the transitions from adenoma to carcinoma stages.
BRAF mutations were found in four villous adenomas (17%) and in the large majority of serrated lesions (81-92%), but were absent in tubular and tubulovillous adenomas.
A BRAF mutation was present in 82% of serrated carcinomas (SCas), 62% of serrated adenomas (SAs), 83% of serrated polyps with abnormal proliferation (SPAPs-syn. sessile serrated adenoma [SSA]), 76% of microvesicular serrated polyps (MVSPs), and was not found in any of the histologic categories of the traditional adenoma-carcinoma sequence.
BRAFV600E mutation analysis was performed in 148 selected cases; mutations were found in 44/49 (90%) of lesions diagnosed as sessile serrated adenoma, in 10/34 (29%) of hyperplastic polyps of microvesicular type, in 4/11 (36%) of traditional serrated adenomas, in 10/10 (100%) of mixed hyperplastic adenomatous polyps, and in 2/42 (5%) of "conventional" adenomas.