The purpose of this study is to test an experimental approach called cell therapy for neuroblastoma or retinoblastoma. This study will take a patient's own white blood cells (T cells) and change them to turn against the cancer. These cells are an experimental treatment and have not been approved by the FDA. CAR T cells have been used to treat other cancers, but GPC2 CAR T cells have not been administered to human patients prior to this clinical trial.

If they choose to participate in this study, active participation will last approximately 12 months. Participants will also be asked to sign consent to a separate long term follow-up protocol to monitor their health for up to 15 years after their last GPC2 CAR T treatment.

This study will assess the safety and effectiveness of GPC2 CAR T cells. Overall, approximately 45 subjects will be enrolled on this study.

This study involves an investigational cellular therapy called Afamitresgene Autoleucel. The overall goal of this study is to find out how safe and effective this cellular therapy is in treating people that have been diagnosed with synovial sarcoma, malignant peripheral nerve sheath tumors (MPNST), neuroblastoma or osteosarcoma that has grown or returned after being treated.

This study enrolls patients with newly diagnosed differentiated thyroid cancer (papillary thyroid cancer or follicular thyroid cancer) that has spread to the lungs and has a genetic mutation called and NTRK fusion. The study involves taking a study drug called larotrectinib for approximately 6 months prior to receiving radioiodine therapy (RAI). The overall goal of this study is to find out if taking the study drug before RAI works better than receiving RAI alone (the usual standard of care treatment).

This study enrolls patients with newly diagnosed differentiated thyroid cancer (papillary thyroid cancer or follicular thyroid cancer) that has spread to the lungs and has a genetic mutation called RET fusion. The study involves taking a study drug called selpercatinib for approximately 6 months prior to receiving radioiodine therapy (RAI). The overall goal of this study is to find out if taking the study drug before RAI works better than receiving RAI alone (the usual standard of care treatment).