A study was done to quantify the pathologic risk of subsequent breast cancer in women whose biopsies demonstrated proliferative histologic conditions. Out of a total of 10,530 patients, 1408 had biopsies which were classified as bland fibrocystic or hyperplastic. The behavior of the disease in these patients was compared to that of the general screened population. Women whose biopsies reveal hyperplastic disorder, primarily atypical hyperplasia and fibroadenoma, run the greatest risk of getting cancer. For women with atypical hyperplasia the risk is 13 times that of the general population and for those with fibroadenoma it is 3 times greater.