Pathological and biological features of mammographically detected invasive breast carcinomas

The pathological and biological features of a consecutive series of impalpable invasive breast carcinoma, detected by mammography in the prevalent round of the breast screening programme, have been compared with a clinically presenting group of carcinomas in age-matched patients. There was a significantly higher prevalence of tubular carcinomas as well-differentiated infiltrating ductal carcinomas in the mammographically detected group, and a lower prevalence of poorly differentiated infiltrating ductal carcinomas. Lymph node metastasis was found in 6.5% of the impalpable group compared with 53% of the clinical group. The prevalence of oestrogen receptor was much higher in the impalpable group (96%) than in the control group (67%), although there were no significant differences for progesterone receptor. The prevalence of pS2 was also much higher in the impalpable group, as was cathepsin D. This finding is surprising in view of the reported relationship between cathepsin D and poorer survival. p53 and c-erb-2 proteins were detectable in fewer impalpable carcinomas. The mean MIBI (Ki-67) index was lower in the impalpable group (11.6) than in the clinical group (15.25). Within the mammographically detected group there was a significant difference in the MIBI index between tubular carcinomas and the different grades of infiltrating ductal carcinomas, with a wide range in each category but no association with size. The impalpable carcinomas detected by mammography differ from clinically presenting carcinomas in many ways, raising the question of whether a proportion or all would progress (dedifferentiate) with time.