Tu175 - Immunephenotyping of Tumor-infiltrating Immune Cells in the Microenvironment of Breast Cancer

Abstract Text: Breast cancer is a heterogeneous disease where the tumor microenvironment (TMA), including immune infiltrates, plays a pivotal role in disease progression and therapeutic response. This study aimed to characterize immune cell phenotypes in the TMA across molecular subtypes of breast cancer.
Formalin-fixed, paraffin-embedded central tumor tissues from 10 breast cancer patients (5 triple-negative (TN), 3 luminal B, and 2 HER2+) were analyzed. Immunohistochemistry was performed for CD8, CD20, FOXP3, PD1, and HLA-DRα markers. Slides were digitized, and quantitative analysis was conducted using QuPath software (version 0.5.1). Cell segmentation and classification were achieved through a neural network, differentiating immune, fibroblast, and tumor cells. A stain intensity classifier provided percentages of positive cells for each marker.
Preliminary results revealed distinct immune profiles among subtypes. TN tumors exhibited the highest HLA-DRα positivity (52.9%) and significant infiltration of CD8+ (25.6%) and PD1+ (15.3%) cells. Luminal B tumors showed elevated CD8+ (32.7%) and FOXP3+ (10.8%) expression but lower PD1+ (3.6%) levels. HER2+ tumors displayed notable FOXP3+ (17.7%) positivity alongside reduced CD8+ (14.9%) and HLADRa+ (29.7%) expression.
These findings highlight molecular subtype-dependent variations in immune cell infiltration. Elevated HLA-DRα in TN and higher FOXP3 in HER2+ suggest differential immune modulation, potentially influencing prognosis and therapeutic strategies. Ongoing studies aim to validate these markers as predictive tools in the evolving era of immuno-oncology, with the goal of advancing personalized treatment strategies based on immune contexture.