Predictors of Lymph Node Metastasis and Prognosis in pT1 Colorectal Cancer Patients with Signet-Ring Cell and Mucinous Adenocarcinomas.

BACKGROUND/AIMS: The local excision of early colorectal cancer is limited by the presence of lymph node metastasis (LNM). Signet-ring cell carcinomas (SRC) and mucinous adenocarcinomas (MAC) are two relatively infrequent histological subtypes. However, little is known about the predictors of LNM and prognosis to support the feasibility of local excision in early-stage SRC and MAC.

METHODS: The Surveillance Epidemiology and End Results Database were used to identify all patients with pT1 adenocarcinomas, including conventional adenocarcinoma (AC), MAC, and SRC. The prevalence of LNM was assessed, and the long-term survival rate in the above three types of colorectal cancer was calculated.

RESULTS: SRC accounted for 0.3% and MAC accounted for 4.4% of the entire cohort of colorectal adenocarcinomas. Compared to AC, MRC and SRC were more often located in the proximal colon, and exhibited a higher grade. The incidence of LNM in AC, MAC, and SRC was 10.6%, 17.2%, and 33.3% for colon cancers and 14.8%, 25.9%, and 46.2% for rectal cancers, respectively. In patients with lymph nodes resected no less than 12, incidence of LNM in AC, MRC, and SRC was 12%, 21%, and 44% for colon tumors and 17%, 30%, and 14% for rectal tumors, respectively. Although, colon patients MAC showed an entirely worse survival rate than AC, rectum patients MAC showed a similar prognosis to AC. We found that in patients with rectal tumors, SRC had a worse 3 and 5-year prognosis than AC. However, for colon cancers, the prognosis of SRC was similar to that of AC. Histology was not found to be an independent prognostic factor in multivariate survival analysis.

CONCLUSIONS: MAC and SRC are two distinct subtypes of colorectal cancer that require special attention despite their relatively rare prevalence. pT1 patients with SRC of the rectum and patients with MAC of the colon have higher incidences of LNM, and with these adverse outcomes, local excision is not recommended. AlthoughMAC of the rectum and SRC of colon have a high rate of LNM, the prognosis of these types are similar to that of AC.