Introduction: Carcinoma of the breast is the most common malignancy of women in Karachi. The currentstudy was conducted with the objective of assessing estrogen receptor (ER), progesterone receptor (PR) andHER-2/neu reactivity patterns of mammary cancers for correlation with histologic grade, tumor size and lymphnode metastasis. Materials and methods: One hundred and fifty modified mastectomy specimens received atthe section of histopathology, Aga Khan University Hospital, were selected using a non-probability samplingmethod. Results: Mean age of the patients was 48.3 years (95%CI 46.5, 50.2). The left breast was more commonlyinvolved (57%). Tumor size ranged from 0.3 to 15.0 cm; 12% were ≤2.0 and 35.3% were ≥ 5.0 cm in diameter.The predominant morphology was infiltrating ductal carcinoma (85.3%). The majority of the cases presentedas grade II (55.3%) lesions with tumor necrosis (70%) and lymph node involvement (71.3%). ER and PR werepositive in 32.7% and 25.3% cases respectively. HER-2/neu was positive (3+) in 24.7%. ER positivity increasedand HER-2/neu positivity decreased with rising age. ER and PR expression was significantly lower in HER-2/neu positive as compared with HER-2/neu negative tumors (ER 83.8% vs 69.8%; PR 91.9% vs 77.8%). In theHER-2/neu positive tumors, ER and PR expression in high grade tumors was significantly decreased comparedwith intermediate grade tumors (ER 5.6% vs 10.5; PR 0% vs 5.3%). ER expression in the HER-2/neu positive,large sized tumors was also significantly decreased compared with smaller tumors (ER 6.3% vs 11.8). Conclusions:ER and PR expression in breast cancers in the current study was found to be comparable to publishedinternational data, but the frequency of HER-2/neu expression was higher, possibly reflecting a young age atdiagnosis. Assessment of prognostic markers for the clinical management of breast cancer patients is stronglyadvocated to provide best therapeutic options.