Clinicopathological study of the colorectal mucinous carcinomas

Histopathologically, the incidence of mucinous carcinomas in Europe and the United States is approximately 10% and that in Japan is low, at 2.9% to 7.4%. The prognosis of mucinous carcinomas is generally thought to be poor, but their clinical and histological features are not well known. In this study, we attempted to clinicopathologically characterize colorectal mucinous carcinomas. Of the 607 colorectal cancer patients, a group of 20 mucinous carcinoma patients (3.3%) and a group of 553 control patients were included in this study. The mucinous carcinomas were subclassified into the following two types to analyze clinicopathological parameters and outcomes: the papillotubular (PT) type and the mucocellular (MC) type. Clinicopathologically, the MC type showed higher rates of venous invasion, lymph node metastasis, liver metastasis, and peritoneal dissemination and higher frequencies of TNM stage III and IV cancers than the PT type. The MC type had a significantly poorer 3-year survival rate of 27% compared with 60% for the PT type. The MC-type mucinous carcinomas showed a significantly higher expression rate (37.5%) of MMP-9 than that (16.6%) in the PT-type mucinous carcinomas. Overall, the colorectal mucinous carcinomas progressed more rapidly and had a poorer prognosis than the control (nonmucinous) cancers. The histological subclassifications MC and PT tended to be molecular-biologically different, and the MC type was poorer in terms of clinicopathological parameters and outcomes.