a method is provided for aid in the diagnosis of breast cancer . nipple aspirate fluid is collected from the breast via a modified breast pump device . breast epithelial cells and proteins present in naf are isolated . nucleic acid is extracted from the becs . the nucleic acids and secreted proteins are analyzed via a low - density nucleic acid and peptidic biopolymeric array , respectively . the level of rna transcription , protein expression , and heterozygosity is compared to that of normal control cells . this invention has particular application to the early detection of breast cancer and the study of individual responses to chemo - and radiotherapeutic exposures .