Invasive lobular carcinoma: an understudied emergent subtype of breast cancer

Invasive lobular carcinoma (ILC) is the second most common histologic subtype of breast cancer after invasive ductal carcinoma (IDC), accounting for 10–15% of all breast cancer cases. Although most ILCs are of the luminal A intrinsic subtype, with favorable prognostic features, conflicting literature data are available on their outcomes compared to IDC with reports suggesting a higher risk of distant recurrence after 10 years. Historically, studies have combined ILC and IDC, with outcomes largely driven by the behavior of IDC given that it represents 90% of breast cancers. However, over the past 5 years, reports of several studies aimed at understanding ILC at the clinical, cellular, and molecular levels have been published, showing that IDC and ILC are distinct entities. In this review, we highlight the unique characteristics of ILC and describe the need for dedicated ILC clinical trials.