npj Breast Cancer publishes original research articles, reviews, brief communications, matters arising, meeting reports and hypothesis generating observations which could be unexplained or preliminary findings from experiments, novel ideas or the framing of new questions that need to be solved. Featured topics of the journal include imaging, immunotherapy, molecular classification of disease, mechanism-based therapies largely targeting signal transduction pathways, carcinogenesis including hereditary susceptibility and molecular epidemiology, survivorship issues including long-term toxicities of treatment and secondary neoplasm occurrence, the biophysics of cancer, mechanisms of metastasis and their perturbation and studies of the tumor microenvironment.