Relationship between mucin expression of gastric intramucosal signet ring cell carcinoma and its background mucosa

The intramucosal lesion of gastric signet ringcell carcinoma (SIG) is known to form a layeredstructure (LS) that simulates mucin expressionin ordinary gastric mucosa. In this study,we suspected the influence of backgroundmucosa on the formation of LS and performedhistopathological analysis. We examined 35 casesof intramucosal SIG with a maximum diameter of30 mm or less. The LS patterns were classifiedinto those with a layer of MUC6-positive cells(complete pattern, CP) and those lacking thislayer (incomplete pattern, ICP). The relationshipbetween LS patterns and the characteristicsof the background mucosa, the expression ofMUC2 (intestinal-type mucin antigen), MUC5AC(foveolar-type mucin antigen), and Ki-67 (themarker of cell proliferation activity) was examinedby histochemistry and immunohistochemistry.Intestinal metaplasia in the background mucosaand MUC2 expression were frequently observedin cases with ICP. Ki-67-positive cells were muchmore and they were distributed more widely inthe lesion of cases with ICP alone than in theother cases. Mucin expression and LS formationof gastric SIG are strongly influenced by itsbackground mucosa. The cases completelylacking MUC6 expression may have highermalignant potential.