The gross cystic disease fluid protein-15/prolactin inducible protein (GCDFP-15/PIP): expression in malignant and non-neoplastic breast tissue

Abstract

GCDFP-15/PIP expression in the breast is regulated by a variety of hormones and is a marker of apocrine differentiation. GCDFP-15/PIP expression in malignant and surrounding non-neoplastic breast tissue was assessed using both Northern blotting and immunohistochemistry in a series of 50 surgical resections performed for the treatment of primary breast cancer. GCDFP-15/PIP mRNA was detected by Northern blotting in 14 50 (28%) carcinomas. Positive immunohistochemical reactions for GCDFP-15/PIP using the monoclonal antibody BRST-2 were observed in 24 50 (48%) carcinomas. None of the carcinomas exhibiting immunohistochemical evidence of gene expression displayed obvious morphological features of apocrine differentiation. Immunohistochemistry was the more sensitive method of detection of gene expression, particularly when only small numbers of tumour cells were expressing GCDFP-15/PIP. GCDFP-15/PIP mRNA was detected by Northern blotting in 15 36 (42%) of samples of macroscopically normal breast tissue from the surrounding breast. Immunohistochemical evidence of GCDFP-15/PIP expression was also frequently observed in normal ductal and lobular epithelium adjacent to the carcinoma. On the basis of these results it is concluded that functional apocrine differentiation occurs more frequently in both normal and malignant breast tissue than might be suspected on morphological grounds. The mechanisms responsible for the induction of GCDFP-15/PIP gene expression in both normal and malignant tissues in breasts harbouring a malignancy remain unclear, but it is possible that they are related.