Assessment of the need and appropriate method for testing for the human epidermal growth factor receptor-2 (HER2)

The human epidermal growth factor receptor-2 (HER2) gene (also known as c-e rbB-2 or neu) is amplified in 20-30% of breast cancers. HER2 gene amplifica tion and HER2 overexpression occur early in the development of breast cance rs and are found in a high proportion of ductal carcinomas in situ (DCIS), non-invasive cancers that generally do not give rise to metastases. In DCIS , HER2 overexpression is found specifically in poorly histologically differ entiated disease and not in well differentiated cancers. Various methods ha ve been used to analyse the HER2 status of a tumour. These either measure t he degree of HER2 gene amplification, receptor overexpression or the amount of circulating HER2 protein. In practice, immunohistochemistry is the most . frequently used method, being available as a standard technique in all pa thology laboratories. It is of critical importance to standardise the metho ds used for staining and to apply common interpretation criteria to enable direct comparison of results between laboratories. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.