This review discusses the parallels between epithelial-mesenchymal transition (EMT) in normal development and cancer progression. EMT and its reverse, mesenchymal-epithelial transition (MET), are critical processes in embryonic development, allowing for complex body patterning and morphogenesis. In cancer, EMT is associated with tumor progression, particularly in breast, ovarian, colon, and esophageal cancers. The review highlights the involvement of key regulators such as Snail/Slug, Twist, Six1, and Cripto, which are misexpressed in breast cancer and correlate with poor clinical outcomes. The authors also discuss the role of collective migration in epithelial cell movement during development and its relevance to cancer metastasis. They emphasize that EMT in cancer is often incomplete and reversible, and that the reactivation of developmental programs in cancer may offer new therapeutic targets. The review concludes by detailing the molecular pathways and transcription factors that are misexpressed in breast cancer, including the Msx2/Cripto pathway and the E-cadherin repressors Snail, Slug, and Twist, which play crucial roles in both development and cancer progression.This review discusses the parallels between epithelial-mesenchymal transition (EMT) in normal development and cancer progression. EMT and its reverse, mesenchymal-epithelial transition (MET), are critical processes in embryonic development, allowing for complex body patterning and morphogenesis. In cancer, EMT is associated with tumor progression, particularly in breast, ovarian, colon, and esophageal cancers. The review highlights the involvement of key regulators such as Snail/Slug, Twist, Six1, and Cripto, which are misexpressed in breast cancer and correlate with poor clinical outcomes. The authors also discuss the role of collective migration in epithelial cell movement during development and its relevance to cancer metastasis. They emphasize that EMT in cancer is often incomplete and reversible, and that the reactivation of developmental programs in cancer may offer new therapeutic targets. The review concludes by detailing the molecular pathways and transcription factors that are misexpressed in breast cancer, including the Msx2/Cripto pathway and the E-cadherin repressors Snail, Slug, and Twist, which play crucial roles in both development and cancer progression.