ABCB1 and breast carcinoma: Serum markers of cancer (neuron-specific enolase, carcinoembryonic antigen (CEA), cancer antigen 125, cytokeratin fragment 21-1) were measured by an automated electrochemiluminescence system and molecular markers (multidrug resistance protein 1, LDL receptor-related protein, ribonucleotide reductase M1, epidermal growth factor receptor, excision repair cross-complementing gene 1, and breast cancer 1) were measured by immunohistochemistry of the primary tumors and metastatic lymph nodes.