Benign mastopathies constitute a very heterogeneous group of breast disorders in which various intricate pictures on the clinical as well as on the histological level are frequently (if not usual) observed. This explains the difficulties in drawing a classification which would be an answer to the clinician's diagnostic and therapeutic preoccupations. Mastopathies said to be "at risk" constitute a sub-group in which the forms can possibly evolves from a benign lesion into a cancer. They have been identified only about fifteen years ago (for example, the works of Haagensen, Wellings and Rywlin). Their definition, their incidence and especially their significance in terms of risk of breast cancer have been described with precision by W.D. Dupont and D. Page in 1985. They consist of proliferating mastopathies with atypical hyperplasia. The knowledge of these mastopathies at risk has logically opened the perspective of a primary prevention of breast cancers by their treatment. Unfortunately, the first difficulty appears right away: one cannot prescribe a treatment without a diagnosis, or that of epithelial hyperplasias rest only on anatomopathological criteria in the absence of radiological and clinical signs or pathognomonic scans. Therefore, the diagnosis is always the result of a preliminary surgical action whose indications are varied and non specific. The second difficulty rests on the fact that there is no certainty that the mastopathies "at risk" constitute a compulsory link in the passage from a normal cell to a cancerous one.(ABSTRACT TRUNCATED AT 250 WORDS)