Morphological and molecular biological features of the mammary gland: a modern view

When identifying breast diseases, differential diagnosis of non–cancerous and tumor conditions, it is necessary to take into account the immunophenotypic profile of epitheliocytes – the expression of receptors for estrogen, progesterone, HER2/neu, the level of proliferative activity, the status of intercellular junctions, as well as the state of immunocompetent cells and other markers. This is especially important for a pathologist when examining biopsy and surgical material, as well as an oncologist when developing treatment and prevention tactics. Purpose of the study . Generalization of data from specialized scientific literature on histological, molecular biological, molecular genetic features of the structure and functioning of the mammary gland, its development and hormonal regulation. Materials and methods . The research for literary sources was carried out mainly by using the PubMed, Google Scholar, Google Books databases, and was limited to the publication date from 2003 to 2024. The following keywords were applied: «mammary gland», «breast», «luminal cells», «myoepithelial cells», «ER», «PR», «HER2/neu», «binucleated cells», «immunohistochemistry», «crown-like adipocytes». Results. For the correct differential diagnosis of pathological conditions, it is necessary to take into account the structural features of the lobular unit of the terminal duct, which change during the menstrual cycle, pregnancy and lactation. The immunophenotypic profile of cells is also of important diagnostic and therapeutic importance, varying depending on the hormonal background – the production of receptors for estrogen, progesterone, proliferative activity, HER2/neu status, the presence of intercellular contacts, etc. In addition, immune cells are necessary for the adequate functioning of the breast. They provide local anti–infective and antitumor immunity, proper formation and involution of lobular units of terminal ducts, elimination of dead cells and apoptotic bodies. Conclusions . The information provided contributes to the adequate verification of malignant neoplasms and other breast diseases in the first place, which is necessary for the pathological examination of biopsy and surgical material, as well as for an oncologist when prescribing specialized therapy.