Clinicopathological features and survival outcomes of primary signet ring cell and mucinous adenocarcinoma of colon: retrospective analysis of VACCR database.

BACKGROUND

Signet ring cell carcinoma (SRCC) accounts for less than 1% of all colon cancers. We examined the clinicopathological features and prognosis of signet ring cell and mucinous adenocarcinoma (MCC) of colon.

METHODS

A total of 206 patients diagnosed with SRCC from 1995 to 2009 were identified from the VA Central Cancer Registry (VACCR) database. Age, race, histology, grade, lymph node status, stage and type of treatment received data were collected.

RESULTS

Out of 206 patients, 173 (84%) were white, 31 (15%) were black, and 2 patients were listed as unknown. Median age of diagnosis was 67 years as compared to 70 years for both mucinous cell (MCC) and non-mucinous adenocarcinoma (NMCC) of colon. Pathological T-stages were as follows: T1 =3%, T2 =5%, T3 =34%, T4 =26%, and unknown 32%. Of the total, 22.3% were located in cecum, 7.7% in appendix, 21.8% in ascending colon, 7.7% in hepatic flexure of colon, 11% in transverse colon, 2.9% in splenic flexure 4.4% in descending colon, and 15.5% in sigmoid colon. 46.5% were lymph node positive, 21% were lymph node negative, and 32.5% were unknown. SRCC were in general poorly differentiated tumors (57%), small proportion of patients included were well-differentiated tumors with focal signet ring cell pathology (10%) and in 33% grade was unknown. Among stage 3 patients, 34% patients received only surgery while 64% received surgery with adjuvant chemotherapy and 2% received chemotherapy alone. The stage specific 5-year survivals for SRCC, MCC and NMCC were--Stage I: 100%, 61%, and 41% respectively (P<0.0001); Stage II: 42%, 58% and 32% respectively (P<0.0001); Stage III: 19%, 41% and 47% respectively (P=0.0002); Stage IV: 1.5%, 7% and 31% respectively (P<0.0001). Median survival of SRCC compared to NMCC was 18.6 vs. 46 months (P<0.0001) and mucinous cell adenocarcinoma versus NMCC was 47.8 and 46 months (P=0.63) respectively.

CONCLUSIONS

SRCC of colon has poor survival rates compared to other histological subtypes. SRCC presents at an earlier age, has higher tumor grade and advanced stage at diagnosis when compared to mucinous and NMCC of colon. Due to rarity of this disease further prospective multi-institute studies are required for in-depth understanding of this disease.