A series of morphological and molecular factors can be used in order to appreciate the prognostic of mammary cancer. A multitude of molecular factors has been investigated in order to identify a prognostic factor, one of the most studied factors being HER2 (human epidermal receptor growth factor). For this purpose, we have carried out an immunohistochemical research, in order to determine the correlation between the presence of morphological factors in tumor formation, different stages of evolution, and the response to therapy. We have correlated HER2 expression with the histological type of carcinomas, the histological differential degree, ER, PR immunohistochemical expression, as well as the available clinical data. Within the studied carcinomas, we have identified a number of 98/156 (62.8%) carcinomas HER2/neu negative, out of which 74/156 (47.4%) did not reveal the presence of HER2/neu and 24/156 (15.4%) have been quantified as being 1+. The HER2/neu supraexpression was encountered in 58/156 (37.17%) cases: in 34/156 (21.8%) cases the immunostaining was interpreted as being 2+ and in 24/156 (15.4%) cases it was interpreted as being 3+. HER2/neu supraexpression should be routinely determined through immunohistochemical methods in all primary mammary tumors, especially in those poorly differentiated.