A COMPARISON BEWEEN RADIOLIGAND AND IMMUNOHISTOCHEMICAL ASSAY OF HORMONE RECEPTORS IN PRIMARY BREAST CANCER

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Abstract
The detection of oestrogen and progesterone receptor (ER and PgR) levels in human breast carcinoma has traditionally been performed using a biochemical radioligand binding method. This method has several disadvantages including the requirement for generous tissue samples, the production of radioactive waste products and the inability to exclude non-malignant cellular material from the assay process. An alternative method for detecting hormone receptors is available with the use of a monoclonal antibody specific for the ER or PgR receptor using immunocytochemical assay (ER-ICA or PgR-ICA). Although designed for use on frozen section material, with modifications this method can be used on paraffin sections of routinely fixed and processed tissue, on archival material and on very small specimens. Further, an objective assessment or scoring of staining intensity is possible using computerized video-image analysis. Forty-three cases of primary breast carcinoma, treated from 1989 to 1991 at Goulburn Valley Base Hospital, Shepparton were assessed for ER and PgR content using both the radioligand method and immunohistochemistry with video-image analysis, and the results were compared. Of the 43 cases, ER-ICA and ER had a concordance of 81% (P < 0.001, r = 0.58) and in 39 cases, PgR and PgR-ICA had a concordance of 87% (P < 0.001, r = 0.54). Because the sample for radioligand assay is of uncertain composition and the immunohistochemical stain can be scored specifically for malignant epithelium, a degree of discordance is thought to be mostly attributable to the limitations of the radioligand assay.