AbstractBackgroundThe prognostic value of mucinous adenocarcinomas (MCAs, exhibiting >50% extracellular mucin) of the colorectum, in relation to their anatomic location is not well studied.Materials and MethodsWe compared MCAs (n= 175) with non‐MCAs (NMCAs,n= 1015) and the cancer‐specific survival rates were evaluated, based on their anatomic site, by univariate Kaplan–Meier and multivariate Cox methods. Subsets of these tumors were immunostained for MUC1, MUC2, Bcl‐2, and p53.ResultsMCAs were more commonly found in the right colon, were of high‐grade, and were more prevalent in younger patients (<40 years). They exhibited strong expression of MUC2 and Bcl‐2 and showed less p53 nuclear staining. In contrast, most NMCAs were low‐grade with high expression of MUC1. MCAs of the rectum were associated with poorer outcomes relative to NMCAs (HR 1.85, CI 95% 1.15–2.97), even though the distributions of advanced‐stage tumors were similar.ConclusionLate‐stage disease and age were poor independent prognostic indicators of cancer‐specific deaths across all tumor locations. In summary, rectal MCAs have a poor prognosis.