Patients with variants outside these criteria had FAP-related extracolonic manifestations, colorectal cancer aged <40, somatic KRAS c.34G > T variant in the tumor or a first-degree relative with >10 adenomas.
Twenty-five CRC biopsies and 15 adenoma were analyzed for KRAS mutations by DNA sequencing (Sanger sequencing), and all 50 patients (35 CRCs and 15 adenomas) were evaluated by immunohistochemistry for the CR-1 protein expression.
As a result, a classification model built with methylation of SDC2 and SFRP2, KRAS mutations and hemoglobin showed a sensitivity of 91.4% for colorectal cancer and 60% for adenoma with the specificity of 86.1%.
Altered miR-21, miRNA-148a Expression in Relation to KRAS Mutation Status as Indicator of Adenoma-Carcinoma Transitional Pattern in Colorectal Adenoma and Carcinoma Lesions.
Additionally, we performed multiregional, targeted next-generation sequencing (NGS) of adenomas and unmasked extensive heterogeneity, affecting known drivers such as APC, KRAS and mismatch repair (MMR) genes.
Most of the genes that are commonly associated with colon cancer, including APC, TP53, and KRAS, were all classified as being early driver genes being mutated in both adenomas and carcinomas.
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.
In the univariate analysis, KRAS mutations were associated with the development of metachronous advanced polyps (OR: 2.36, 95% CI: 1.22-4.58; P = 0.011), and specifically, advanced adenomas (OR: 2.42, 95% CI: 1.13-5.21; P = 0.023).
In conclusion, our results indicate that MLH1-hypermethylated BRAF wild-type colorectal carcinomas can harbor KRAS mutations and arise from precursor polyps resembling conventional tubular/tubulovillous adenomas.
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.
P16 staining was lost in the advanced areas of 55% of BRAF mutant traditional serrated adenomas compared with 10% of the advanced areas of KRAS mutant or BRAF/KRAS wild-type traditional serrated adenomas.
Together, this may suggest that two molecular pathways, intermediate methylation associated with KRAS mutations and LST-G morphology, and low methylation associated with CTNNB1 activation and LST-NG morphology, might be involved in LST development, and that involvement of TP53 mutations could be important in both subtypes in the development from adenoma to cancer.
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.
Clinical findings, morphologic features, immunophenotypes and KRAS alterations were investigated in 7 patients with intraductal tubular adenomas, 16 patients with gastric-type intraductal papillary mucinous neoplasms and 6 patients with intraductal tubulopapillary neoplasms.
M2PK showed a detection rate of 40.3% for adenomas but the combination of M2PK and KRAS abnormalities was found in only 5.7% of adenomas (P <0.01). iFOBT was false positive in 31.8% of cases in which colonoscopy excluded neoplastic lesions, while the coexistence of molecular and enzymatic abnormalities was more specific with false positive rates between 8.3% and 9.0% (P <0.05).