Monoclonal antibody 44-3A6 as a marker for breast carcinoma.

The monoclonal antibody (MAb) 44-3A6 detects a 40-kD cell surface protein on adenocarcinomas and may serve as an effective marker for glandular differentiation. Immunohistochemical analysis of 123 paraffin-embedded malignant breast tissue specimens, 27 normal or benign breast disease specimens and 10 atypical hyperplasia specimens from patients without breast cancer was performed with MAb 44-3A6. The antigen was identified in 76% of breast cancer specimens, 0% of normal or benign breast disease specimens and 88% of the atypical hyperplasia specimens. MAb 44-3A6 also detected this antigen on adjacent normal breast ductal cells in 88% of the breast cancer specimens. There was no statistically significant correlation between immunoreactivity and histological mitotic or nuclear grade, recurrence or overall survival. This study suggests that the cell surface antigen detected by the MAb 44-3A6 may serve as an important marker in the differentiation of normal breast epithelium into an atypical or malignant lesion.