Cathepsin D immunocytochemical assays in breast carcinomas: image analysis and correlation to prognostic factors

Immunocytochemical assays of cathepsin D were assessed in a series of breast carcinomas (n = 257) using monoclonal M1G8 anti-total cathepsin D and the avidin-biotin-peroxidase complex. Cathepsin immunoreactivity was compared in frozen and paraffin sections. All tumours were anti-cathepsin-positive. Positive staining was observed in carcinoma and stromal cells and in the extracellular matrix. The amount of immunodetectable cathepsin in tissue was measured by computer-assisted image analysis (SAMBA 2005). Both the percentage of immunostained tumour surface and the mean optical densities were processed as continuous variables for statistical analysis and correlated with prognostic factors. It was shown that cathepsin D was independent of the tumour size, the lymph node status, hormone receptors, and pHER-2/neu overexpression. Cathepsin was significantly correlated with anti-EGFR (P = 0.012) and Ki67 (P = 0.002) immunoreactivity, tumour grade (P = 0.032), vascular invasion (P = 0.0081), proliferation index (P = 0.0045), and, to a lesser extent with AgNORs (P = 0.0504) and the degree of hyperploidy (P = 0.057). Tissue fixation and paraffin embedding significantly decreased cathepsin immunoreactivity. These results show that cathepsin D is not a totally independent prognostic factor in breast carcinomas.