The prognostic significance of two epithelial membrane antigens expressed by human mammary carcinomas.

As many patients with mammary carcinoma are now treated by conservative forms of surgery, there is a need for prognostic information obtainable from the primary tumour alone. One possible source is the antigenic profile of tumour cells. Using an indirect immunoperoxidase technique, we stained histological sections of the primary tumour from 175 patients with each of two monoclonal antibodies (HMFG-1, HMFG-2), raised against milk fat globule membrane antigens known to be preserved in formalin-fixed tissues. Sections were assessed by light microscopy as to both the overall distribution of antigen expressed and its site in tumour cells. The findings were related to relapse-free survival by life-table analysis. The median duration of follow-up was 36 months. Two patterns of staining with antibody HMFG-1 gave information of prognostic significance but staining with HMFG-2 was without significance. Complete absence of staining with HMFG-1 in 13 patients was associated with an extremely poor prognosis and 10 (77%) of these patients developed metastases within 18 months of follow-up (p less than 0.001). Extracellular staining (ECS) in 22 patients, however, was associated with a favourable prognosis. As assessed by a semi-quantitative method, only one patient (5%) demonstrating a high level of ECS developed metastases (p less than 0,004). These two patterns were analysed for a relationship to other prognostic indicators. Absence of staining was independent of histological grade, tumour size, axillary lymph node status and menopausal status. ECS was associated with low histological grade although this relationship was not absolute. In addition to their use in diagnosis, we conclude that monoclonal antibodies such as HMFG-1 may be useful as prognostic indicators.