Nonmetastatic Axillary Lymph Nodes Have Distinct Morphology and Immunophenotype in Obese Patients with Breast Cancer at Risk for Metastasis

Abstract

Obese breast cancer patients have worse outcomes than their normal weight counterparts, with a 50% to 80% increased rate of axillary nodal metastasis. Recent studies suggest a link between increased lymph node adipose tissue and breast cancer nodal metastasis. Further investigation into potential mechanisms underlying this link may reveal potential prognostic utility of fat-enlarged lymph nodes in breast cancer patients. This study uses a deep learning model to identify morphological differences in non-metastatic axillary nodes between obese, node-positive and node-negative breast cancer patients. The model was developed using nested cross-validation on 180 cases and achieved an AUC of 0.67 in differentiating patients using hematoxylin and eosin stained whole-slide images. The top predictive patches from the slides according to the model were reviewed by a pathologist and their morphological differences were quantified. This analysis showed an increased average adipocyte size (p-value=0.004), increased white space between lymphocytes (p-value<0.0001), and increased red blood cells (p-value<0.001) in non-metastatic lymph nodes of node-positive patients. Preliminary immunohistochemistry analysis on a subset of 30 patients showed a trend of decreased CD3 expression and increased leptin expression in fat-replaced axillary lymph nodes of obese, node-positive patients. These findings suggest a novel direction to further investigate the interaction between lymph node adiposity, lymphatic dysfunction, and breast cancer nodal metastases, highlighting a possible prognostic tool for obese breast cancer patients.