Increasing evidence supports the importance of the role of pregnancy, lactation and post-weaning breast remodeling in the etiology of certain types of early onset aggressive breast cancers, including basal breast cancers, which are difficult to detect and treat and disproportionately affect African American women. Thus, improving methods for detecting or preventing early onset tumors is important from a clinical, public health and racial disparities perspective. Recent evidence indicates that analysis of breast milk during the postpartum period may advance the discovery of mechanisms and biomarkers related to risk of early onset, aggressive tumors. However, developing methods for collecting, processing and testing milk for biomarkers poses challenges.