Prognosis of mucinous and signet-ring cell colorectal cancer in a population-based cohort

Besides classical colorectal adenocarcinomas (AC), mucinous adenocarcinomas (MAC) and signet-ring cell carcinomas (SC) occur. Controversy remains regarding their prognostic role. Aim of this study was to define prognostic and histopathological specifications of mucinous and signet-ring cell colorectal cancer. A total of 28,056 patients with AC, MAC, and SC between 1998 and 2012 in the catchment area of the Munich Cancer Registry were analyzed. Time to locoregional recurrence and distant recurrence was calculated by cumulative incidence. Survival was analyzed by the Kaplan-Meier method, calculation of relative survival, and Cox proportional hazards regression. AC occurred in 25,172 patients (90 %), MAC in 2724 (9.7 %), and SC in 160 (0.6 %). AC were less frequently localized in the proximal colon (34 %) compared to MAC (57 %, p < 0.001) and SC (76 %, p < 0.001). Both, MAC and SC had higher T, N, and M categories, lymphatic invasion, and worse grading (p < 0.001 for each). There were significant differences regarding the 10-year cumulative incidence of locoregional recurrence (p < 0.001), and distant recurrence (p < 0.001). For AC, the 5-year overall survival was 59 % (95 % confidence interval 58.0; 59.3), for MAC 52 % (50.2; 54.2), and for SC 40 % (32.1; 48.5; p < 0.001). However, MAC or SC did not remain independent prognostic factors for overall survival compared to AC upon multivariable analysis (p = 0.981). This large cohort reveals specific histopathological and recurrence patterns for patients with colorectal AC, MAC, and SC. MAC and SC are diagnosed at more advanced tumor stages and therefore entail reduced survival rates.