[Detection of HER-2/neu in breast carcinoma]

HER-2/neu protein overexpression has been shown to be an independently adverse prognostic and predictive factor in patients with breast cancer. Recently, HER-2/neu overexpression has gained therapeutic implications: It has been shown that in patients with breast cancer the use of trastuzumab/Herceptin TM, the recombinant humanized monoclonal antibody directed against extracellular domain of HER-2/neu molecule, can block the HER-2/neu protein activation and bring about a clinical remission. Following these developments, demand for pathologists to evaluating properly HER-2/neu in breast cancer specimens has been rapidly increasing.

In our series of 449 cases of breast cancer, HER-2/neu protein and gene were examined by means of immunohistochemistry and fluorescence in situ hybridization respectively. Results of HER-2/neu study were compared with the hormonal status, cancer grade and proliferation activity as assessed using immunohistochemistry with MIB1 antibody. All seven cases of breast cancer with strong overexpression of HER-2/neu (score 3+) manifested a gene amplification. In contrast, among 11 cases of breast cancers with mild HER-2/neu overexpression (score 2+), the gene amplification was demonstrated in 5 cases only (45%).

Immunohistochemical assessment and fluorescence in situ hybridization (FISH) are complementary methods for detection of HER-2/neu status in breast cancer. While immunohistochemistry is an excellent screening method, FISH should be used for the confirmation of positive results before the Herceptin treatment.