Chronic mastopathy and breast cancer. A follow-up study.

Over an average period of seven years 2,9000 cases of benign breast lesions diagnosed by biopsy between 1948 and 1973 in the Department of Pathology, Kaiser Foundation Hospital, Oakland, were followed for breast cancer development. When classified according to traditional diagnostic categories, the cancer incidence per 1,000 person-years varies between 2.7 and 7.9 and appears to be elevated in comparison to expectations obtained from the Third National Cancer Survey, San Francisco Bay Area. Two thousand four hundred biopsies were also scored by the Black-Chabou method. There is an upward trend in the breast cancer incidence as the atypia score rises, a finding which confirms conclusions from a retrospective case-control study by Black et al.