Immunohistochemical expression of BRCA1 protein in invasive ductal carcinoma of the breast.

Immunohistochemically detected BRCA1 positivity has been reported to indicate the presence of full-length functional protein, while immunohistochemical negativity may be a result of sporadic BRCA1 mutation. We set out to study the immunohistochemical expression of BRCA1 protein in breast cancer and assess associations with lymph node status, histologic grade and expression of other biomarkers. We examined 100 patients aged from 21 to 71 years diagnosed with invasive ductal carcinoma. Immunohistochemistry was performed using anti-BRCA1, ER, PR, HER2/neu, and Ki-67 (MIB-1) antibodies. Cytoplasmic or nuclear-cytoplasmic BRCA1 expression was identified in a total of 64 breast cancer patients. None of the breast cancer tissue samples showed solely nuclear BRCA1 immunoreactivity. BRCA1 expression was associated with higher histologic grade, and majority of BRCA1-positive patients were below 50 years of age. Most BRCA1-negative patients had intermediate grade tumors. BRCA1 expression was positively associated with ER and PR positivity, and negatively associated with HER2/neu overexpression. Although immunohistochemistry can be an inexpensive and valuable preliminary method for detecting the BRCA1 status, BRCA1 protein localization is a complex issue. Well designed studies are needed to further investigate the performance of various anti-BRCA1 antibodies in formalin- fixed paraffin-embedded tissue samples, assess their association with BRCA1 gene mutations and determine clinical usefulness of BRCA1 immunohistochemistry.