Sclerosing adenosis and infiltrating epitheliosis are both benign diseases which are clinically, radiologically and macroscopically impossible to distinguish from cancer. Over a four years' period, 27 lesions of this kind, which are usually considered as rare, were found in 27 patients. The average age of the patients was 36 years, which confirmed the lesions as diseases typical of fertile women. In all cases, both clinical and instrumental findings (mammography and echotomography) indicated a kind of malignant cancer. The final diagnosis was always made on surgical/bioptic (fine-needle biopsy) specimens. This paper is aimed at stressing the lack of mammographic findings useful for the differential diagnosis of sclerosing adenosis-infiltrating epitheliosis and breast cancer. The utility of fine-needle aspiration biopsy is also stressed.