However, to predict Trastuzumab activity, it is essential to verify the availability of the Trastuzumab target epitope, especially since several studies have demonstrated the occurrence of tumours expressing variants of the HER-2 protein (Christianson et al, 1998; Kwong and Hung, 1998; Molina et al, 2001, 2002). Here, ERBB2 is linked to neoplasm.