For the development of a dual-labeled tracer for image-guided surgery, we conjugated trastuzumab with both a radioactive (111In) and fluorescence (IRDye800CW) label and determined the biodistribution, performed micro-SPECT/CT and fluorescence imaging and image-guide surgery in an orthotopic HER2-positive breast cancer model. This evidence concerns the gene ERBB2 and breast carcinoma.