Identification of HER-2/neu Protein Expression in the Breast Cancer

Overview

Background.
HER-2/neu protein overexpression has been shown to be an independently adverse prognostic andpredictive factor in patients with breast cancer. Recently, HER-2/neu overexpression has gained therapeuticimplications: It has been shown that in patients with breast cancer the use of trastuzumab/HerceptinTM, therecombinant humanized monoclonal antibody directed against extracellular domain of HER-2/neu molecule, canblock the HER-2/neu protein activation and bring about a clinical remission. Following these developments, demandfor pathologists to evaluating properly HER-2/neu in breast cancer specimens has been rapidly increasing.Methods and Results. In our series of 449 cases of breast cancer, HER-2/neu protein and gene were examined bymeans of immunohistochemistry and fluorescence in situ hybridization respectively. Results of HER-2/neu studywere compared with the hormonal status, cancer grade and proliferation activity as assessed using immunohistochemistrywith 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 %).Conclusions. Immunohistochemical assessment and fluorescence in situ hybridization (FISH) are complementarymethods for detection of HER-2/neu status in breast cancer. While immunohistochemistry is an excellent screeningmethod, FISH should be used for the confirmation of positive results before the Herceptin treatment.

Key words:
breast cancer, HER-2/neu, oncoprotein cerbB2, immunohistochemistry, FISH.