Benign breast lesions and subsequent breast carcinoma in Rochester, Minnesota.

Case histories of 444 female patients (Rochester residents) with benign breast disease pathologically diagnosed between 1935 and 1949 were studied prospectively for the development of breast cancer. After exclusion of unsuitable cases, 370 remained for review of pathologic diagnoses and statistical analysis. Breast cancer developed in 14 (3.8%) within a median period of 13.5 years after the diagnosis of benign breast disease. Most of these malignancies occurred within 10 years after the original diagnosis. Patients in whom the original diagnosis was chronic cystic mastitis developed breast cancer 2.9 times more frequently than expected. Breast cancer developed 10 times as often as expected in those patients of ages 40 to 49 at the time of diagnosis of breast malignancy. This evidence shows that a more intensive follow-up of patients with confirmed chronic cystic breast disease is justified, especially among those of ages 30 to 49 years.