Mouse models that faithfully recapitulate human cancers are indispensable tools for studying the molecular mechanisms of tumorigenesis and testing potential anticancer therapies. In this issue of Cancer Cell, Derksen et al. describe a new mouse model that mimics multiple features of invasive lobular carcinoma of the breast (ILC), a histological subtype of human breast cancer for which no mouse model currently exists. This model further reveals an important causal link between E-cadherin loss and tumor initiation and metastasis and, in doing so, provides a valuable entrée into the tumor-suppressive functions of E-cadherin as well as the molecular underpinnings of ILC.