Breast cancer (BC) is the most frequent malignancy among women worldwide and has been associated with high mortality because of the late treatment of the disease. Our group has proposed a selective ablation of breast cancer cells by the use of magnetic fields assisted by magnetic nanoparticles. The principle is to increase the conductivity of tumoral tissue by the use of a bioconjugated "nanoparticle-antibody" that recognizes specific antigens on the surface of the cancer cells. The aim of this study was to evaluate the c-erbB-2 antigen in breast cancer cells of type BT-474, MCF-7, and MDA-MB-231 as a possible target for the use of magnetic nanoparticles coupled to a specific Monoclonal Antibody (Mab). Quantitative real-time polymerase chain reaction and flow cytometry were used to estimate the relative expressions of the c-erbB-2 gene and the c-erbB-2 antigen in the cell lines, respectively. A covalent union of magnetic nanoparticles to anti c-erbB-2 Mab was used to develop the bioconjugate. Fluorescence microscopy was used to determine the cells that were tagged by the bioconjugate. The results show a well-differentiated relative expression of c-erbB-2 in the studied cell lines and are qualitatively in agreement with the fluorescent marking by the magnetic nanoparticles. The selected breast cancer cells appear to be suitable for experimental evaluation of selective targeting by magnetic nanoparticles.