Abstract
Features of 111 mammary carcinomas derived from breast cancer screening were compared with those of 69 carcinomas presenting 'clinically'. Screen detected cancers were smaller, had less likelihood of nodal metastases, included a higher proportion of in situ tumours and if invasive, tended to be of lower grade. Using immunohistochemical methods, the expression of c-erbB-2 oncoprotein, epidermal growth factor receptor (EGFR) and cathepsin D were compared in the two groups. A similar proportion of screened and unscreened tumours expressed c-erbB-2 oncoprotein and EGFR but expression of the oestrogen regulated protein cathepsin D was significantly more frequent in the screened group (P less than 0.05). Although a relatively small series, the results suggest a biological difference between 'screened' and 'clinical' tumours.