Intrauterine breast development and the mammary myoepithelial lineage

As their name implies, the myoepithelial cells found at the epithelial-mesenchymal interface of the human mammary gland disclose features suggestive of a dual epithelial-like and muscle-like differentiation, i.e. they co-express various keratins and vimentin intermediate filaments, as well as smooth muscle-related antigens. This article provides an overview of the literature on intrauterine breast development with special emphasis on the myoepithelial component of the fetal human mammary gland epithelium. It discusses original and recently published immunohistochemical data on myoepithelial precursors and reasserts the relevance of developmental, morphological fetal tissue-based studies to the understanding and the clinical management of adult diseases.