The apparent increase of incidence of DCIS is related to the development of mammographic screening programs and requires an effort of diagnostic, classification and treatment revision. The same natural history of the DCIS is still poorly known, and the phases of its evolution are supposed essentially on epidemiologic and statistics bases. The efforts for a classification are aimed to the search of a prognostic meaning: nuclear grading and possible invasive evolution; association of nuclear grading and necrosis. Both are correlated with local recurrence and free interval. The finding of micro-calcifications is the basis of the instrumental mammographic diagnosis; the possible isolated and unique finding encourages choices of conservative surgery. But as the less large lesions are as a rule of higher grade than those more extended, there are the treatment can be puzzling. As a consequence in fact the former are exposed to wider resections than the last ones. The DCIS is also characterized in its post-surgical evolution from the borders of the excision, from the pathologic classification, from the nuclear degree and from the dimensions of the lesion. In the more favourable conditions the surgical excision represents an adequate treatment. The radiotherapy finds his role in the more elevated degrees and in the case of incomplete excision, also if only presumptive. The alternative is the reoperation and the mastectomy.