Pathological aspects of the UK Breast Screening Project with special reference to minimal and 'borderline' lesions.

Because of the logistical and financial implications of large scale screening for the early detection of breast cancer, the Department of Health and Social Security in the UK has established a study to compare two methods, mammography and breast self-examination. Screening is under evaluation in women aged 45-64 years, over a seven year period. Mammography is carried out in health districts based on Edinburgh and Guildford and self-examination related to a programme of education in Huddersfield and Nottingham. Four other health districts, Bristol, Dundee, Oxford and Stoke, act as control areas. A Pathology Review Panel composed of pathologists from each participating centre has been established to verify the accuracy of the histopathological data. In particular, all lesions in the borderline between benign and malignant disease are reviewed together with all minimal carcinomas. The Pathology Panel has carried out four consistency surveys to improve diagnostic criteria and accuracy, and 83% agreement is now achieved with no errors across the benign/malignant border. Review of 'borderline' cases from the study is now in progress.