An evaluation of the usefulness of primary tumour expression of MCA and CA15-3 as prognostic indicators in breast carcinoma.

CA15-3 antigen and mucin-like carcinoma associated antigen (MCA) show potential as clinically useful serum markers of breast carcinoma. Recently, immunohistochemical versions of these monoclonal antibodies have become available but few data are available as to their clinical usefulness. The aims of this study were (i) to assess CA15-3 and MCA expression by primary breast tumours and to correlate tumour immunoreactivity with tumour behaviour, and (ii) to investigate the relationship between immunohistological staining and oestrogen receptor (ER) status. Pathological material from 39 stage 1 (node free) breast carcinoma patients was assessed. The mean age was 51.3 (range 34-70) years, 19 were premenopausal and the mean duration of follow-up was 3.6 years (range 0.8-14 years). In each case two further sections were stained with antisera to the CA15-3 and MCA antigens. Staining of primary tumour was achieved in 38 cases. Low (less than 30% tumour cell staining) and intermediate (30-60% of cells staining) grade immunoreactivity with both monoclonals correlated with significantly shorter disease free intervals (P less than 0.05). Neither monoclonal can predict ER status. We conclude that the use of monoclonal antibodies to CA15-3 and MCA in staining primary breast carcinoma tumours and their axillary nodes may be a significant (P less than 0.05) prognostic indicator of future tumour behaviour and that this requires further evaluation.