Integrin alpha6beta4 is mostly expressed in epithelial tissues and endothelial and Schwann cells. Expression of alpha6beta4 is increased in many epithelial tumours, implicating its involvement in tumour malignancy. Moreover, this integrin activates several key signalling molecules in carcinoma cells, but its ability to activate the phosphatidylinositol 3-kinase/Akt pathway is among the mechanisms by which alpha6beta4 integrin regulates tumour behaviour. In this review we discuss the biological and clinical features of alpha6beta4 integrin that allow it to promote tumour survival and progression of mammary tumours.