Dendritic Cell Subpopulations Are Associated with Prognostic Characteristics of Breast Cancer after Neoadjuvant Chemotherapy—An Observational Study

Breast cancer (BC) is the most prevalent malignancy in women and researchers have strived to develop optimal strategies for its diagnosis and management. Neoadjuvant chemotherapy (NAC), which reduces tumor size, risk of metastasis and patient mortality, often also allows for a de-escalation of breast and axillary surgery. Nonetheless, complete pathological response (pCR) is achieved in no more than 40% of patients who underwent NAC. Dendritic cells (DCs) are professional antigen-presenting cells present in the tumor microenvironment. The multitude of their subtypes was shown to be associated with the pathological and clinical characteristics of BC, but it was not evaluated in BC tissue after NAC. We found that highe r densities of CD123(+) plasmacytoid DCs (pDCs) were present in tumors that did not show pCR and had a higher residual cancer burden (RCB) score and class. They were of higher stage and grade and more frequently HER2-negative. The density of CD123(+) pCDs was an independent predictor of pCR in the studied group. DC-LAMP(+) mature DCs (mDCs) were also related to characteristics of clinical relevance (i.e., pCR, RCB, and nuclear grade), although no clear trends were identified. We conclude that CD123(+) pDCs are candidates for a novel biomarker of BC response to NAC.