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

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Abstract
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 tumor alone. One possible source is the antigenic profile of tumor cells. Using an indirect immunoperoxidase technique, histological sections of the primary tumor from 175 patients were stained with each of 2 monoclonal antibodies (HMFG-I, HMFG-2), raised against milk fat globule membrane antigens preserved in formalin-fixed tissues. Sections were assessed by light microscopy as to both the overall distribution of antigen expressed and its site in tumors cells. The findings were related to relapse-free survival by life-table analysis. The medium duration of follow-up was 36 mo. Two patterns of staining with antibody HMFG-I gave information of prognostic significance but staining with HMFG-2 was without significance. Complete absence of staining with HMFG-I in 13 patients was associated with an extremely poor prognosis and 10 (77%) of these patients developed metastases within 18 mo. of follow-up (P < 0.001). Extracellular staining (ECS) in 22 patients, however, was associated with a favorable prognosis. As assessed by a semi-quantitative method, only 1 patient (5%) demonstrating a high level of ECS developed metastases (P < 0.004). These two patterns were analysed for a relationship to other prognostic indicators. Absence of staining was independent of histological grade, tumor 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, monoclonal antibodies such as HMFG-I may be useful as prognostic indicators.