Invasive lobular carcinoma of the breast: Patient response to systemic endocrine therapy and hormone response in model systems

► Invasive lobular carcinoma (ILC) is a critically understudied breast cancer subtype. ► ILC patient outcomes do not correlate with overall favorable biomarkers. ► Little clinical data and few laboratory models exist to study endocrine response in ILC. ► We review the clinical phenotype and current understanding of hormone response in ILC models. ► Understanding endocrine response in ILC is critical to improve patient outcomes.