Objective — to analyze the clinical, morphological, and genetic characteristics of rare breast cancer (BC) forms for their more accurate and timely diagnosis and definition of the tactics of a patient follow-up. Material and methods. A total of 1272 case histories of BC from the Russian X-ray Radiology Research Center in the past 20 years were retrospectively analyzed. Results. The proportion of rare BC forms (tubular, papillary, medullary, cribrous, mucous, and metaplastic carcinomas) was 9.8% (125 cases). All rarely encountered forms of breast cancer were observed in the stage Т1—2N0M0. Stage T3—4 was encountered and the tumors were characterized by a rapid growth in metaplastic carcinoma. The hormone-dependent HER2-negative tumors included papillary, cribrous, mucous, and tubular carcinomas. Two metaplastic carcinoma cases were hormone-negative and HER2-positive. The data of mammography and ultrasonography indicate that the rare forms of BC have often signs of a fibroadenoma exhibiting well-defined rounded outlines and a homogeneous texture; they are frequently avascular and, according to sonoelastographic findings, the deformation coefficient rarely exceeds 2%. Conclusion. Some BC forms may have a more or less positive prognosis than ductal carcinoma, which may affect the choice of tactics for treatment and further monitoring for the patent. Their similarity to benign diseases requires an attentive and qualitative differential diagnosis in order to timely detect a disease. Investigations should be continued, by elaborating new diagnostic and treatment algorithms for patients with rare BC forms.