MRI Features Associated with High and Low Expression of Tumor-Infiltrating Lymphocytes: Stratified Analysis According to Molecular Subtypes

Motivation: Tumor-infiltration lymphocytes (TILs) express variably in different molecular subtypes. Goal(s): To compare the rate of high vs. low TILs and MRI features in three subtypes: Hormonal-Receptor positive, HER2 negative (HR+/HER2-), HER2+, and TN, and compare imaging features in each subtype. Approach: The percentage of TILs of 457 breast cancers was assessed. Three radiologists reviewed MRI features. Results: HER2+ cancers were more likely to present as non-mass enhancement (NME). In HR+, high TILs cases were more likely to present peritumoral edema. In TN, high TILs cases were more likely to present regular shapes and circumscribed margins. Impact: TILs expression increases from HR+ to HER2+ to TN. MRI features in different molecular subtypes show substantial variations. Different models should be built for different subtypes when building MR radiomics models to predict TILs.