Mucinous Differentiation in Colorectal Cancer : Molecular, Histological and Clinical Aspects

Background : Mucinous colorectal carcinoma represents a subtype of colorectal carcinoma (CRC), which is characterized by abundant amount of extracellular mucin. We reviewed the molecular, histological and clinical aspects of mucinous CRC as compared to the non-mucinous type. Methods : A systematic web-based research was performed using Web of Knowledge. The combination of the Boolean search terms "COLO*" AND "MUC*" was used. The literature was searched until July 2013. Results : Patients with mucinous CRC have distinct clinical and pathological features. Mucinous CRC tends to occur in younger patients, are often seen in the proximal colon, are more diagnosed at an advanced stage and are more frequently associated with hereditary non-polyposis colorectal cancer (HNPCC) and young-age sporadic colorectal cancer. The prognostic significance of mucinous differentiation remains uncertain ; some studies have shown a poor response to oxaliplatin and/or irinotecan based chemotherapy. Mucinous CRC is associated with a higher expression of MUC2 and MUC5AC, but a lower expression of MUC1. The differential expression of mucins has been related to altered risk of metastasis and death. Recently, mucins have been used as targets for molecular therapy and as a source of immune therapy. Mucinous differentiation is associated with other specific genetic and molecular features such as increased BRAF mutation rate and microsatellite instability. Conclusion : Mucinous CRC is a distinct clinical, pathological, and molecular entity. The implications of mucinous differentiation for treatment response and outcome are not fully elucidated, but the available data suggest an adverse effect. The use of mucins as immunotargets may show therapeutic promise for mucinous CRC.