Reduction in HER-2 protein expression in a breast tumor HER-2 positive after only one injection of Trastuzumab: A case report

Abstract

HER-2 is overexpressed in 20 to 30% of breast cancer. Generally, metastases of a breast tumor have the same HER-2 status, although some discordances were reported. We report a case of reduction in HER-2 expression assessed by immunohistochemistry, following one day of a Trastuzumab injection, of a metastatic breast cancer to lymph nodes. Initially, the breast tumor HER-2 status was positive according to the same technique. We raise a hypothesis about technical interference and discuss the case in the framework of the existing literature. © 2009 Elghissassi et al; licensee Cases Network Ltd.