Signet ring, high grade, and undifferentiated colorectal adenocarcinomas differ.

Background: Studies with limited sample sizes have found colorectal signet ring carcinoma (SRC), to be prognostically similar to high grade adenocarcinoma (HGA); the relationship of these tumors to undifferentiated adenocarcinoma (UND) has not yet been fully elucidated. This study of Surveillance, Epidemiology, and End Results (SEER) program data compared the histotypes.

Methods: Registered as having been diagnosed between 1988 and 2003 were 2,246 SRC, 32,999 HGA, and 920 UND. Analyses were performed to determine the presence or absence of differences in survival and extent at presentation.

Results: SRC, compared with HGA, was more likely to (1) be confined to an in situ stage or within a polyp, (2) have invaded visceral peritoneum, (3) have spread to contiguous organs, and (4) have metastasized. No differences between SRC and UND were seen, although this may have been due to small UND sample size. SRC was associated with a worse prognosis than HGA for patients with (1) T3 tumors, (2) contiguous organ spread, and (3) visceral peritoneal invasion. UND was associated with a worse prognosis than SRC among patients with metastases.

Conclusions: These three histotypes of aggressive colorectal cancer are separate entities that should be regarded as such. Future study with respect to SRC should include further evaluation of T1 and T2 patients with appropriate sample size populations and the potential utility of peritoneal sampling and frozen section evaluation of non-mucosal margins.