HER-2/neu oncoprotein overexpression in breast cancer patients has an impact on prognosis and treatment methods so assessment of its status is therefore much needed. The study group consisted of 90 cases of mammary invasive carcinoma. The distribution of HER-2/neu immunoexpression for scores 0, 1+, 2+ and 3+ were 54.44%, 11.11%, 18.8% and 15.56% respectively. HER-2/neu -positive cases comprised 21.42% of patients less than 50-year-old compared to 14.47% of patients of 50-year-old or older. Tumor size was negative correlated with HER-2/neu immunoexpression: positive tumors comprised 37.5% of tumor larger than 5 cm and this percentage decreases with tumor dimension to 2.94% in tumors of 2 cm or less. Regarding the histopathological subtype of invasive mammary carcinoma, only some types were positive, like 17.57% of IDC NOS and one case of mixed ductal-lobular invasive carcinoma. The highest proportion (21.31%) of positive HER-2/neu cases presented high-grade carcinomas (GIII), comparing with well-differentiated (GI) that were all negative. Regarding the axillary lymph node status the lowest proportion of positive HER-2/neu cases was 4.54% in the absence of metastasis, and rises to 34.78% in cases with more than three axillary lymph nodes involved. HER-2/neu-positive tumors showed a low incidence of ER+ or PR+ cases unlike HER-2/neu -negative cases (35.71% vs. 83.05% for ER, respective 21.42% vs. 76.27% for PR). Therefore, in conclusion, HER-2/neu-positive tumors are significantly fewer than the negative ones, but these are found in younger women and are associated with: large tumor size, high grade of malignancy (GIII) and increased number of axillary lymph node involvement. HER-2/neu immunoexpression is related to histological subtype of invasive breast carcinomas. Hormonal status is negative related to HER-2/neu expression.