Background: Previous studies have shown conflicting results on the relation between clinicopathologic features and prognosis of patients with colorectal mucinous, signet-ring cell, or non-mucinous adenocarcinoma; only few such studies have been performed in China. This retrospective study analyzed data from our department to investigate clinicopathologic characteristics, prognosis and possible correlations of three histologic types - colorectal mucinous, signet-ring cell, and non-mucinous adenocarcinoma, to clarify the bases for observed differences which may lead to development of targeted therapies.

Methods: Of 2079 patients diagnosed with colorectal cancer between 1994 and 2007, 144 had mucinous, 25 had signet-ring cell, and 1837 had non-mucinous adenocarcinoma. Their clinicopathologic parameters and survival were analyzed using established statistical methodologies.

Results: Mucinous and signet-ring cell adenocarcinomas were common in younger patients (P < 0.001). Location, size and disease stage differed significantly among the three types. Signet-ring cell tumors were more commonly found in the rectum than mucinous and non-mucinous adenocarcinoma (P < 0.001). Mucinous and signet-ring cell tumors presented in a later stage in life more often than non-mucinous adenocarcinoma, with lymph node involvement, serosal infiltration, peritoneal dissemination, and adjacent organ invasion (P < 0.01). The rate of radical resection, hepatic metastasis and local recurrence did not differ among types (P > 0.05). Compared with patients with non-mucinous adenocarcinoma, patients with mucinous and signet-ring cell tumors who underwent potentially curative resections or stage II/III disease had poorer long-term overall survival. Survival did not differ by type for patients with either stage I or IV disease (P > 0.05).

Conclusions: Mucinous and signet-ring cell adenocarcinoma have unique carcinogenesis and similar biologic behavior. Our study confirms that both histologic types, especially signet-ring cell tumors, are independent, negative prognostic factors for patients with colorectal cancer. Type does not appear to have a significant effect on survival when disease is either stage I or IV at presentation.