Presently representing 15 to 30% of new cases of breast cancer, ductal carcinomas in situ do not have specific epidemiological characteristics. The age at which they occur is between 49 and 54 years.The diagnosis is evoked primarily when confronted with an area of micro-calcifications discovered on a mammography. Needle aspiration cytology, useful in cases of palpable abnormalities or infra-clinical masses, is of no interest in isolated micro-calcifications for which surgical biopsy following radiological localisation is the technique of choice. Needle micro-biopsy permits collecting analysable tissue for histological but not cytological examination. Macro-biopsies combine stereotaxic localisation of micro-calcification areas and their excision when isolated. The choice of the method varies depending on the case.Ductal or intra-galactophoric carcinomas are carcinomas of the glactophores that do not infiltrate the connective tissue. They are defined histologically by architectural and cytological characteristics, which differentiate them from lobular carcinomas in situ. They constitute a group of heterogenic lesions not only morphologically but also histologically and with regard to their progression.The aim of treatment is to ensure that the patients have a maximum of chances of cure at the cost of the least possible therapeutic consequences. Mastectomy, treatment of choice for many years, is still recommended in certain situations. In other cases, conservative treatment is possible so long as excision of the micro-calcifications is complete on the post-surgical mammography and, in the case of biopsy excision, that healthy margins of at least 10 millimetres exist. Following surgery, there is no sufficient consensus to propose essential recommendations concerning the place of monitoring alone, irradiation or tamoxifen.