Mapping clinicopathological entities within colorectal mucinous adenocarcinomas: a hierarchical clustering approach

The aim of this study was to interrogate the heterogeneity of colorectal mucinous adenocarcinomas. This study is based on hierarchical clustering approach combining clinicopathological and molecular patterns known to be relevant to oncogenesis and therapeutic management of patients with colorectal carcinoma, ie, microsatellite instability, O6-methylguanine-DNA methyltransferase (MGMT) status, KRAS, and BRAF mutations and wnt signaling pathway activation. Comparison of the study group of 60 mucinous adenocarcinomas defined according to World Health Organization classification with control group of 136 colorectal adenocarcinomas successively removed shows higher frequency of BRAF and KRAS mutations and microsatellite instability-high status and lower frequency of wnt signaling pathway activation in mucinous adenocarcinomas. 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. Age, TNM stage, and BRAF mutation had prognostic value. Hierarchical clustering analysis led to the identification of several clinicopathological entities of colorectal mucinous adenocarcinomas with epidemiologic, prognostic, and therapy relevance. Both KRAS and BRAF mutations appear as drivers in the alternate oncogenetic pathways governing the development of sporadic colorectal mucinous adenocarcinomas.