B7H3 CAR T Cell Immunotherapy for Recurrent/Refractory Solid Tumors in Children and Young Adults

Inclusion Criteria: * Participants age ≤ 26 years at the time of consent for study participation; the first 2 participants enrolled and treated with CAR T cells in both Arms A and B will be ≥ 15 years. and ≤ 26 years at time of consent for study participation * Histologically diagnosed malignant, non-primary CNS solid tumor * Evidence of refractory or recurrent disease * Lansky or Karnofsky score ≥ 50 * Life expectancy ≥ 8 weeks * Recovered from significant acute toxic effects of all prior chemotherapy, immunotherapy and radiotherapy * If no apheresis product or usable T cell product is available, all chemotherapy has been discontinued ≥ 7 days prior to enrollment * If no apheresis or usable T cell product is available, all biologic therapy has been discontinued ≥ 7 days prior to enrollment * If no apheresis product or T cell product is available, all systemic corticosteroid therapy has been discontinued ≥ 7 days prior to enrollment (physiologic replacement dosing is allowed) * If no apheresis product or usable T cell product is available, at least 3 half-lives or 30 days (whichever is shorter) from time of last dose of anti-tumor directed antibody therapy (including checkpoint inhibitor) at time of enrollment * If no apheresis product or usable T cell product is available, at least 6 weeks post last dose of myeloablative therapy and autologous and/or allogeneic stem cell transplant, or non-myeloablative therapy and allogeneic stem cell transplant (all timed from stem cell infusion). Participants who receive autologous stem cell infusion following non-myeloablative therapy are eligible once all other eligibility requirements are met. * If no apheresis product or usable T cell product is available, participants who have received genetically modified cell therapy must be at least 30 days from most recent cell infusion prior to enrollment * If no apheresis product or usable T cell product is available, participants with neuroblastoma must be at least 12 weeks from I131 MIBG therapy. * Adequate organ function * Adequate laboratory values * Participant is able to tolerate apheresis (including placement of temporary apheresis catheter, if necessary), or already has an apheresis product available for use in manufacturing. * Participants of childbearing potential must agree to use highly effective contraception Exclusion Criteria: * Presence of active malignancy other than primary malignant solid tumor diagnosis * Current relevant CNS pathology * Receiving external beam radiation therapy at time of enrollment * Presence of active GVHD, or receiving immunosuppressive therapy for treatment or prevention of GVHD within 4 weeks prior to enrollment * Participant is pregnant or breastfeeding * Participant has presence of active severe infection * Participant has presence of any condition that, in the option of an investigator, would prohibit the participant from undergoing treatment under this protocol * Participant has primary immunodeficiency syndrome * Unwilling or unable to provide consent/assent for participation in the study and 15 year follow up period