THE INFLUENCE OF MAMMOGRAPHY SCREENING ON THE PATHOLOGICAL PANORAMA OF BREAST-CANCER

The pathologist describes the biological domain of breast cancer in wh ich the clinician works. Over the last 20 years there have been indica tions that the biological domain has shifted following the introductio n of fine-needle biopsies, clinical mammography, and later screening m ammography. The most commonly used parameters for staging, classificat ion and grading of cancer in some respects probably reflect the biolog ical domain. We describe how the pathological panorama of breast cance r has changed with the introduction of population-based mammography sc reening. Our experiences are based on a consecutive series of 1961 bre ast cancers diagnosed from 1977 to 1994 in a region where screening ma mmography was introduced in 1988. All results, including histological classification and grading were prospectively registered in a computer ized data base. There were more comedo than tubuloductal carcinomas an d there was a corresponding preponderance of grade LII tumours in the youngest and a high incidence of tubuloductal, lobular and colloid can cers in the oldest age group. The proportion of women with comedo carc inoma decreased after 1987. Looking at changes in the grade distributi on after 1987, the proportion of women with grade I tumours increased and grade III tumours decreased in women over 50 years of age, but in the youngest women only marginal changes were noted. Very few in situ carcinomas were diagnosed in the prescreening period. About 11% of all tumours were in situ after 1987. The percentage of node-positive canc er decreased in the screening period in all histological types of canc er regardless of tumour size. The percentage of small tumours less tha n or equal to 20 mm increased with time, though less so for comedo car cinomas. Comedo carcinomas dominate among the largest cancers most fre quently detected clinically. From a biological standpoint it is intere sting to note that screening seems to entail a larger shift in the bio logical domain in older as compared to younger women. Furthermore, com edo carcinomas seem to be less well detected by the screening procedur e.