NCAM1 and synovial sarcoma: CD56 can be targeted by the ADC lorvotuzumab mertansine that has shown only limited efficacy in a phase 2 study in children with relapsed or refractory Wilms tumor, rhabdomyosarcoma, neuroblastoma, pleuropulmonary blastoma, malignant peripheral nerve sheath tumor or synovial sarcoma [33,34].