Oestrogen receptor activity in breast cancer detected at a prevalence screening examination.

In view of the possible introduction of screening programmes, this study compares oestrogen receptor (ER) levels in a series of women whose primary tumour was detected by screening and an age-matched consecutive series of women whose tumours were diagnosed after symptomatic presentation. Because of missing data and other statistical considerations, the comparison was made using T1 and T2 categories of tumour only. Some differences were found: the distribution of ER levels was significantly different in the two groups, with more extreme values in the symptomatic series; the screening series, however, had more moderate/rich ER levels than the symptomatic group. Tumours of special pathological type (for example, tubular, cribriform, lobular, medullary, and mucoid) were more likely to be ER-moderate or -rich, and there were more of these tumours in the screening series. The relationship of these findings to tumour growth rate is discussed. The study highlights the difficulty of obtaining sufficient tissue for conventional DCC biochemical assays from the small non-invasive tumours found by screening, and suggests that newer alternative methods employing monoclonal antibodies may be required for such types of tumour.