Correlation of MUC5AC immunoreactivity with histopathological subtypes and prognosis of gastric carcinoma

Background: MUC5AC represents a mucin peptide core expressed in normal gastric epithelia. Its presence in gastric carcinomas was previously described as a characteristic of gastric differentiation. Methods: MUC5AC reactivity was investigated by immunohistochemistry and correlated with clinicopathological variables in a large series (n = 200) of gastric carcinomas. Results: A statistically significant association between MUC5AC positivity and parameters of cancer progression (pTNM staging and grading) could not be observed. However, MUC5AC exhibited correlations with certain subtypes of histopathological differentiation. A significant reduction of MUC5AC expression was evident in mucinous and undifferentiated carcinomas according to the World Health Organization classification, as well as in type III cancers according to the Goseki classification system. Furthermore, reduced MUC5AC reactivity (confined to up to 35% of the tumor area) was significantly correlated with an unfavorable prognosis of all patients in univariate and multivariate analysis. The same association could be observed in the subgroup of pTNM stage 1 patients (n = 60). Conclusions: A significant reduction of gastric differentiation as reflected by MUC5AC immunoreactivity represents a marker of worse survival probability in gastric cancer. Finally, reduced MUC5AC positivity defines a high-risk subgroup of pTNM stage 1 patients.