Influence of Mucinous and Signet-Ring Cell Differentiation on Epidemiological, Histological, Molecular Biological Features, and Outcome in Patients with Colorectal Carcinoma

Background: Colorectal cancer (CRC) is one of the most common malignancies in the Western world. Histopathologically, adenocarcinomas are mostly diagnosed. Mucinous and signet-ring cell subtypes occur with a very low incidence. However, these subtypes differ remarkably in terms of clinical, histological and molecular biological characteristics. The aim of this review is to present a detailed analysis of current knowledge regarding differences between classical adenocarcinoma and mucinous, and signet-ring cell CRC along with potential consequences for daily practice. Methods: For this report all articles with relevant information on differences between classical adenocarcinoma and mucinous, and signet-ring cell CRC found via Pubmed searches were analysed. Furthermore, findings of our previous study were included. Results: Mucinous CRC occur with a reported incidence of 10-20% in Western countries and are predominantly found in younger patients and females. They are more often diagnosed in the proximal colon and present with a higher stage at diagnosis. Furthermore, there is a higher rate of lymph node-positive tumours and peritoneal carcinomatosis. Results of molecular biological studies confirm that they may represent a different tumour entity. The response to well established chemotherapy regimens is poorer which may be attributed to the higher rate of microsatellite-instable tumours and an increased mucin secretion. The poorer outcome is likely related to the higher stage at the time of diagnosis. Signet-ring cell type CRC are rare with an incidence ranging between 0,9% to 4%. They are also more common in the right colon and are associated with a poorer outcome compared to adenocarcinoma and mucinous CRC. Conclusions: However, it should be noted that most of the results come from studies with avery low number of patients which can be attributed to the low incidence of mucinous and signet-ring cell CRC. Based on the findings of the present analysis, a more radical surgical approach should be considered providing that the exact preoperative histology is available. Furthermore, the histological subtype should be taken into account in future chemotherapy trials to avoid unnecessary therapy. A closer follow-up, especially for patients with signet-ring cell CRC should be discussed. In the near future, a more tailored therapy in patients with colorectal cancer would be highly desirable.