Co-expression and prognostic value of gross cystic disease fluid protein 15 and mammaglobin in primary breast cancer.

Gross cystic disease fluid protein (GCDFP-15) and mammaglobin are both widely used and accepted markers for epithelia of breast origin. We aimed to evaluate their relation of expression on parallel whole tissue sections in primary breast cancer by immunohistochemistry and also to correlate it with clinico-pathological parameters including patient survival. Primary breast carcinomas from 165 patients with a mean clinical follow-up of 73 months were immunostained using commercially available antibodies against GCDFP-15 and mammaglobin. An immunoreactive score (IRS) was calculated based on the cytoplasmic staining intensity and the number of cells stained. Cytoplasmic expression of GCDFP-15 and mammaglobin was observed in 73.3% and 72.1% of invasive breast carcinomas respectively. 91.8% of breast cancer cases expressed at least one of both markers. Both markers strongly correlated with each other and were significantly associated with lower tumour grading. Additionally, GCDFP-15 negativity was significantly associated with shortened disease-free survival times in univariate and multivariate analyses. We demonstrated the strong correlation of GCDFP-15 and mammaglobin with each other and showed that only very few primary breast cancers are completely negative for both markers. The significantly longer disease free survival times for patients with GCDFP-15 positive tumours clearly warrants further study.