- Participants must have invasive primary tumor or metastatic tissue confirmation of HER2-positive status, defined as presence of one or more of the following criteria: Over-expression by IHC with score of 3+ AND/OR HER2 gene amplification (> 6 HER2 gene copies per nucleus or a FISH ratio [HER2 gene copies to chromosome 17 signals] of ≥ 2.0) Note: Participants with a negative or equivocal overall result (FISH ratio of <2.0 or ≤ 6.0 HER2 gene copies per nucleus) and IHC staining scores of 0, 1+, 2+ are not eligible for enrollment.