- Either the primary tumor or the metastasis must overexpress HER2; acceptable methods of measurement of HER2 expression include immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH); tumors tested by IHC must be 3+ positive for HER2 overexpression using the DAKO Herceptest or the CB-11 antibody (recently FDA approved for HER-2 testing); tumors tested by FISH must be positive by either the Vysis Pathyvision method or the Ventana INFORM method; patients may have measurable or evaluable disease