Gastric carcinoma metastatic to the breast diagnosed by mucosubstance histochemistry and electron microscopy.

Bilateral breast tumors with a histologically scirrhous pattern were conclusively diagnosed as gastric carcinoma metastatic to the breast using mucosubstance histochemistry and electron microscopy. The majority of the carcinoma cells gave histochemically positive reactions for galactose oxidase-Schiff, stable class III con A, and high-iron diamine-alcian blue (HID-AB). Also electron microscopically, numerous HID-positive mucus droplets (sulfomucin) were seen in the carcinoma cells. These findings invalidated the possibility that the carcinomas were primary breast cancer. The practical applications of distinctive patterns of mucus secretion are discussed.