Abstract 1912: Immune and molecular markers in benign breast disease predict risk of node-positive breast cancer

Abstract Background: Breast cancer (BC) remains a leading health concern worldwide and is often undetected until it metastasizes, limiting treatment options and worsening prognosis. Early detection of molecular and immune markers in benign breast disease (BBD) could identify women at elevated risk of developing invasive, node-positive BC, enabling targeted surveillance and prevention efforts. Building on this premise, we investigated the immune and molecular landscape of BBD biopsies preceding BC development to enhance risk stratification and inform preventive strategies. Methods: Utilizing the Mayo Clinic BBD cohort, we conducted a case-control study comparing women who developed node-positive BC following their BBD biopsy (cases; n=8) to those who remained cancer-free (controls; n=11), matched on patient age and biopsy date. Differential gene expression was assessed using the NanoString nCounter system to identify differentially expressed genes between cases and controls. We developed a multiplex immunofluorescence (MxIF) approach using the Opal system by Akoya Biosciences for comprehensive marker detection in formalin-fixed, paraffin-embedded (FFPE) tissue samples. Digitized images were segmented for cell phenotyping, and spatial relationships of immune cells were analyzed and compared between cases and controls. Results: Our findings revealed significantly increased expression levels of immunosuppressive genes in the case group, including CD48, CD84, IL-32, and LAIR1. Immunohistochemical analyses showed that controls exhibited higher frequencies of CD68+ (macrophages), CD11c+ (M1 macrophages), and CD206+ (M2 macrophages) cells compared to cases. Notably, controls had a significant increase in CD68+CD11c+ cells, indicative of a pro-inflammatory, antitumorigenic M1 macrophage polarization. Furthermore, our MxIF analyses provided novel insights into spatial biomarker localization, enhancing prognostic accuracy. Conclusions: The decreased numbers of immune cells and increased expression of immunosuppressive genes in BBD biopsies may be associated with an elevated risk of developing axillary node-positive BC. These findings emphasize the importance of dissecting molecular and immune interactions in BBD for risk assessment. Our results have the potential to improve individualized risk stratification, leading to more targeted surveillance and informed screening. This research not only contributes to our understanding of BC pathogenesis but also opens avenues for developing novel preventive strategies, potentially reducing BC incidence and mortality through early intervention. Citation Format: Matilde Rossi, Nicole Cruz-Reyes, Trista Navarro, Melody L. Stallings-Mann, Bryan M. McCauley, Robert A. Vierkant, Stacey J. Winham, Mark E. Sherman, Amy C. Degnim, Derek C. Radisky. Immune and molecular markers in benign breast disease predict risk of node-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1912.