A 10-year outcomes evaluation of mucinous and signet-ring cell carcinoma of the colon and rectum.

PURPOSE: Most studies examining mucinous or signet-ring cell colorectal cancers are single institution reports. This study used a national cancer registry to analyze the epidemiology and survival outcomes of these two subtypes of colorectal cancer compared with adenocarcinoma tumors.

METHODS: All patients diagnosed with mucinous (n = 16,991), signet-ring cell (n = 1,522), or adenocarcinoma (n = 146,115) colorectal cancer in the Surveillance, Epidemiology, and End Results database (1991-2000) were evaluated. Analyses were performed to obtain age-adjusted incidence rates, stage at presentation, tumor grade, and five-year relative survival for each subtype.

RESULTS: Mucinous were slightly more common in females (53.4 percent). Incidence rates per 100,000 persons were: mucinous, 5.5; signet-ring cell, 0.6; and adenocarcinoma 46.6. The annual percent change during ten years was stable for mucinous, increased for signet-ring cell (4.8 percent; P < 0.05), and decreased for adenocarcinoma (-1.1 percent; P < 0.05). Fewer mucinous (18 percent) and signet-ring cell (21 percent) tumors were located in the rectum compared with adenocarcinoma (29 percent). Signet-ring cell presented at later stage (III/IV, 80.9 percent) more often than mucinous (52.8 percent) and adenocarcinoma (49.5 percent), and also had worse tumor grade (high grade: signet-ring cell, 73.5 percent; mucinous, 20.9 percent; adenocarcinoma, 17.5 percent). Relative five-year survival was worse for signet-ring cell than mucinous or adenocarcinoma.

CONCLUSIONS: We present a large population-based review of colorectal cancer subtypes by analyzing national data from the past decade. Although the incidence of colorectal adenocarcinoma is decreasing in the United States, mucinous and signet-ring cell subtypes are stable and increasing, respectively. Importantly, it seems that the signet-ring cell subtype has worse outcomes, whereas survival rates for mucinous tumors are similar to adenocarcinomas.