Identification of a lower grade muconodular subtype of gastric mucinous cancer

Until now, survival analysis of gastric mucinous cancers showed either no difference or an even worse prognosis than stage-adjusted non-mucinous tumours. In the pancreas and breast, mucinous cancers showing well-demarcated mucin deposits (muconodular pattern), expansile growth and predominance of MUC2 mucin are known to have a more favourable prognosis. In this study, an attempt was made to separate, among 41 gastric mucinous cancers, a subgroup of tumours with muconodular expansile pattern, possibly predictive of a more favourable outcome. A group of 15 tumours was identified, which were characterised by overwhelming (80-100%) mucinous component, predominance of mucus over tumour cells inside muconodules, moderately aggressive growth of their epithelial component (reduced proliferative rate, moderate anaplasia, lack of angioinvasion and limited lymphoinvasion) and dominant expression of intestinal goblet cell markers, with special reference to MUC2 mucin. Univariate and multivariate survival analysis showed a significantly improved outcome of these lower grade muconodular tumours compared with the remaining mucinous cancers as well as with non-mucinous cancers of cohesive, diffuse (signet-ring cell included) and undifferentiated high-grade types.