Invasive lobular carcinoma (ILC) is the most common special subtype of breast cancer, accounting for 10%-15% of all breast cancers, which represents ~26-40,000 cases annually in the US. There is an increasing recognition that ILC has distinct clinical, histologic, molecular, and biological characteristics compared to IDC. The hallmark of ILC is the loss of E-cadherin, resulting in a more linear growth pattern of cells as compared to round masses usually seen in IDC. This unique growth pattern is associated with challenges in detection of ILC. Despite favorable prognostic factors, long-term outcome for patients with ILC is worse compared to those with breast cancer of no special type (NST) (previously called invasive ductal cancer, IDC). In this presentation, I will present an overview of biological and clinical differences, and also highlight current efforts to improve understanding of the disease with the goal of subtype-tailored therapy.