Relationships Between MRI Breast Imaging‐Reporting and Data System (BI‐RADS) Lexicon Descriptors and Breast Cancer Molecular Subtypes: Internal Enhancement is Associated with Luminal B Subtype

The aim of this study was to determine the associations between breast MRI findings using the Breast Imaging‐Reporting and Data System ( BI ‐ RADS ) lexicon descriptors and breast cancer molecular subtypes. In this retrospective, IRB ‐approved, single institution study MRI s from 278 women with breast cancer were reviewed by one of six fellowship‐trained breast imagers. Readers reported BI ‐ RADS descriptors for breast masses (shape, margin, internal enhancement) and non‐mass enhancement (distribution, internal enhancement). Pathology reports were reviewed for estrogen receptor ( ER ), progesterone receptor ( PR ), and human epidermal growth factor receptor‐2 ( HER 2). Surrogates were used to categorize tumors by molecular subtype: ER / PR +, HER 2‐ (luminal A); ER / PR +, HER 2+ (luminal B); ER / PR ‐, HER 2+ ( HER 2); ER / PR / HER 2‐ (basal). A univariate logistic regression model was developed to identify associations between BI ‐ RADS descriptors and molecular subtypes. Internal enhancement for mass and non‐mass enhancement was combined for analysis. There was an association between mass shape and basal subtype (p = 0.039), which was more frequently round (17.1%) than other subtypes (range: 0–8.3%). In addition, there was an association between mass margin and HER 2 subtype (p = 0.040), as HER 2 cancers more frequently had a smooth margin (33.3%) than other subtypes (range: 4.2–17.1%). Finally, there was an association between internal enhancement and luminal B subtype (p = 0.003), with no cases of luminal B cancer demonstrating homogeneous internal enhancement versus a range of 10.9–23.5% for other subtypes. There are associations between breast cancer molecular subtypes and lesion appearance on MRI using the BI ‐ RADS lexicon.