Mucinous gastric cancer presents with more advanced tumor stage and weaker β-catenin expression than nonmucinous cancer

Background: Mucinous gastric carcinoma (MGC) is a rare type of gastric cancer; its biological behavior is controversial. In this study, we attempted to clarify the clinical and pathological features as well as the prognostic significance of MGC. We also compared the expression patterns of CDX-2 and β-catenin between MGC and nonmucinous gastric carcinoma (NMGC). Methods: We reviewed the records of 9218 patients with gastric cancer who underwent gastric cancer surgery between January 1997 and December 2006. The clinicopathological features and clinical outcome of MGC (n = 197) were compared to NMGC (n = 9021). Immunohistochemical staining using the tissue array method was performed on MGC (n = 194) and NMGC (n = 89) tissues. Results: MGC had a larger size and a higher frequency of Borrmann type I findings in advanced cases than NMGC. In addition, MGC had deeper invasion, more lymph node and lymphatic involvement, a more advanced tumor stage, and lower 5-year survival rates than NMGC. Age, depth of invasion, lymph node metastasis, lymphatic invasion, and curability were independent prognostic factors; but the mucinous histological type itself was not predictive of outcome. β-Catenin immunoreactivity was statistically significantly weaker in MGC than NMGC; however, there was no difference in CDX-2 expression between the two groups. Conclusions: MGC presents at a more advanced stage and was larger than NMGC. The poor prognosis of MGC was related to the more advanced tumor stage at diagnosis; the histological type was not an independent prognostic factor. The result of immunohistochemical staining suggests that MGC has a distinct pathway of carcinogenesis from NMGC.