We and others have shown that malignancies that express HER2 at low levels can be targeted with T cells that express HER2-CARs [13], and recently implemented a phase I clinical study using HER2-CAR T cells for the immunotherapy of HER2-positive sarcomas [5], with most patients enrolled having a diagnosis of osteosarcoma. This evidence concerns the gene ERBB2 and osteosarcoma.