Introduction: Breast cancer is the leading cause of death in women due to malignant tumors. Invasive breast carcinoma of no special type with medullary pattern accounts for only 1% of all types cancers. Immunohistochemical diagnosis of medullary breast cancer is a leading factor in determining the prognosis and selection of treatment for this type of neoplasia. The study of the microenvironment of the tumor evaluates the aggressiveness of the tumor. The presence of inflammatory infiltrate has been shown to reduce the invasive and metastatic properties of the tumor. On the other hand, the presence in the tumor-associated environment of M2 macrophages that exhibit prooncogenic and angiogenic properties is a prognostically unfavorable sign for the course of the neoplastic process.

Aim: Study of immunohistochemical features of medullary carcinoma for the presence of M2 macrophages.

Materials and methods: Invasive breast carcinoma of no special type with medullary pattern, immunohistochemical investigation of breast cancer tissue.

Results: Immunohistochemical examination of the microenvironment of medullary carcinoma of the breast revealed a significant number of macrophages, among them a significant proportion were M2-macrophages (CD163 + cells), which were diffusely localized in all components of tumor tissue.

Conclusions. The presence of M2 macrophages in the tumor-associated microenvironment of tumor cells suggests a prognostic-adverse effect on the course of the neoplastic process of medullary carcinoma of the breast. Detection of these markers shows tumor aggressiveness, increased activity in angiogenesis and invasive growth.