Effect of tumour size on the association between pS2 and cathepsin D in primary breast cancer

Previous studies have shown that pS2 and cathepsin D are linked in lymph node positive (N+) tumours, but not in tumours from lymph node negative (N-) patients. The purpose of this study was to understand whether or not size would effect the relationship between pS2 and cathepsin D. Findings were further extended to some subgroups of tumours obtained stratifying for T and N and particularly to the small (TI) but aggressive (N+) cancers (T1/N+) and to those of size greater than 2 cm (T2 and T3) but yet node negative (T2+T3/N-). Oestrogen (ER) and progesterone (PR) receptors, pS2 and cathepsin D concentrations were therefore assayed in 355 primary breast cancers. ER, PR, pS2 and cathepsin D did not correlate to nodal status and size of the tumours; no significant differences in the expression of these four biological factors between infiltrating ductal carcinomas without special features (NOS) and non-NOS carcinomas were found. Multivariate analysis performed among cathepsin D, ER, PR and pS2 indicated that, in T1 tumours, pS2 was the most important variable and the best predictor in cathepsin D determination, while such association was absent in T2 and T3 tumours. pS2 and cathepsin D significantly associated also in tumours obtained from N+ patients, and such correlation was highest in T1 tumours with positive axillary nodes (N+/T1). pS2 and cathepsin D did not associate in tumours taken from N- patients. Considering the NOS carcinomas, correlation between pS2 and cathepsin D in the N+, T1 and N+/T1 subgroups was higher in the poorly differentiated grade 3 with respect to grade 1 and grade 2 cancers. The data suggest that pS2 could have a role in cathepsin D expression and we hypothesise that such control could be an early biological event occurring in the development and progression of particularly aggressive (N+/grade 3), small (T1) breast cancers.