There are a few studies that have evaluated a panel of stains on a single large data set of breast cancers, which is required for direct comparison between antibodies. The immunohistochemical panel in this study was chosen to include breast-specific markers and markers that are expressed in tumors resembling breast cancer. The individual marker positivity in decreasing order was 95% (177/186) for GATA-3, 92% (172/186) for cytokeratin (CK)7, 80% (151/189) for AR, 80% for estrogen receptor (158/198), 69% for progesterone receptor (137/198), 55% (105/190) for NY-BR-1, 52% (99/189) for mammaglobin, 31% (59/191) for vimentin, 26% (51/195) for GCDFP-15, 0.5% (1/186) for CK20, and 0% (0/188) for PAX-8. When tumors were categorized based on estrogen receptor and HER2 status; a total of 45 profiles were identified. In addition, some tumors showed an unconventional profile-although the majority of breast carcinomas were CK7-positive/CK20-negative, a CK7-negative/CK20-negative profile was seen in ∼8% of the cases. Such a profile can create confusion in investigation of a carcinoma of unknown origin. The results define the individual sensitivity of each marker and establish a baseline diagnostic profile of breast cancer in a large data set. In addition, the results support the use of immunohistochemical panel for confirming or determining breast as the source of metastasis.