Preneoplastic lesions in the human breast.

A subgross sampling technique with histological confirmation was used to study the pathology of 119 whole human breasts, either cancer-associated (that is, containing cancer or contralateral to a cancer) or taken from random routine autopsies. Atypical lobules were observed much more frequently in the cancer-associated group than in the group of routine autopsy breasts. Atypical lobules showed varying degrees of anaplasia that formed a continuum between normal epithelium and carcinoma in situ, usually of the common ductal type. As apprarent markers for increased cancer risk, atypical lobules in the human breast may be homologous to hyperplastic alveolar nodules that are abundant in high mammary cancer strains of mice. This indirect evidence supports the hypothesis that atypical lesions are common preneoplastic lesions in the human mammary gland.