Lymphoid environment in molecular subtypes of breast cancer

Recently, a large body of evidence has shown that the microenvironment of invasive breast carcinoma affects its development and the patient’s outcome, and vice versa – cancer cells express factors that modulate tumour milieu in terms of its composition and function. We performed an immunohistochemical (IHC) staining of 108 formalin-fixed, paraffin-embedded (FFPE) tissue samples to investigate the relationships between T-cell, B-cell, and NK-cell infiltrate, invasive breast carcinomas molecular subtypes, and other prognostic indicators. The main findings of our study were as follows: the significantly higher infiltrate of the analysed immune cell subsets in triple-negative (TNBC), HER2-positive, non-luminal and luminal B/HER2+ breast carcinomas than in luminal A cancers; their higher densities in poorly differentiated lesions; correlations between lymphoid cells and the expression of hormonal receptors, HER2 receptor status, and marker of cancer proliferation. Furthermore, we observed T-cell numbers to be associated with greater tumour diameter. In summary, the results of our study indicate associations between tumoural lymphoid infiltration and the unfavourable intrinsic subtypes as well as other detrimental prognostic factors in invasive breast carcinomas.