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.
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