Clinical significance of signet ring cell rectal carcinoma

Signet ring cell carcinoma of the rectum (SCCR) is a rare type of rectal carcinoma. This study examined the clinical significance of SCCR.

From our medical records we retrospectively identified 61 SCCR patients and compared their clinical data and outcomes to those of 144 consecutive patients with non-SCCR mucinous rectal adenocarcinomas (NSMR) and 2,414 consecutive patients with nonmucinous rectal adenocarcinomas (NMR).

The incidence of SCCR was 1.39% of rectal cancers. Mean patient age at onset of SCCR (48.1years, range 15–80) was significantly lower than that for NSMR (57.4 years, 9–88) and NMR (62.6 years, 12–94). The proportion of late stage (TNM III+IV) tumors was significantly higher in SCCR (90%) than in NSMR (69%) and NMR (48%). There were more tumors located in the lower rectum in SCCR (46%) than in NSMR (34%) and NMR (29%). SCCR tumors were significantly larger (5.68±3.84 cm) than NSMR (4.27±1.78 cm) and NMR tumors (3.76±1.71 cm). A higher percentage of patients with SCCR (42.6%) received abdominoperineal resection for treatment. In tumors with TNM stage IV the rate of tumor spread via the hematogenous route was significantly lower in SCCR (18.5%) than in NSMR (43.5%) and in NMR (69%). The rate of tumor spread via seeding to the peritoneum was lower in SCCR (22.2%) than in NSMR (43.5%) but higher than in NMR (2.7%). The rate of tumor spread via the lymphatic route was higher in SCCR (44.4%) than in NSMR (26.1%) and significantly higher than in NMR (12.3%). The 1-, 2-, and 5-year overall SCCR survival rates were 73.9%, 36.3%, and 23.3% respectively, which were significantly poorer than those of NSMR and NMR. For the 28 stage III and R0 SCCR tumors the 1-, 2-, and 5-year disease-free survival rates of SCCR were 84.0%, 44.2%, and 30.3%, respectively, which are comparable with general data of stage III rectal cancer in the world.

Diffuse infiltration of signet ring cells enhances the tendency of mucinous carcinomas of the rectum in more local extension and easier lymphatic spreading but not at peritoneal seeding. Although SCCR had the poorest prognosis, this outcome may be due to the advanced tumor stage rather than histology itself.