The aim of our work was to determine the expression of glycoprotein 96 (gp96; glucose-regulated protein 94 - GRP94) in 69 samples of breast carcinoma. Enzyme immunohistochemical method was chosen for the detection of gp96 protein and its expression was compared in breast cancer cells versus normal breast cells. We found higher expression of gp96 protein in breast carcinoma cells and low or no expression in normal breast cells. Furthermore, we demonstrate first time, that ductal invasive breast carcinomas showed higher expression of gp96 than lobular invasive breast carcinomas.