Pedi-STAR: Surface Target Antibody-drug Conjugate (ADC) Antigen Expression in Relapsed/Refractory Pediatric Solid and CNS Tumors

Inclusion criteria

Inclusion Criteria for Prospective Cohort * Age 0 - 30 years at time of initial diagnosis of the solid or CNS tumor * Diagnosis of relapsed or refractory solid or CNS tumor, without a limit on the number of prior episodes of relapse. Refractory disease is defined as disease that progresses on standard-of-care upfront therapy or requires salvage therapy due to inadequate response, e.g. bridging chemoimmunotherapy in a patient with high-risk neuroblastoma and poor end-induction response (PEIR). * Life expectancy of at least 12 weeks at the time of enrollment * Available specimens Tissue block or unstained slides available expected to yield a minimum of 30 total slides., OR other specimens expected to result in adequate (1) RNA quantity and quality for sequencing and (2) IHC testing may substitute for tissue requirement above with the approval of the PI or study staff designee approval prior to submission enrollment. Tumor tissue from relapse/progression is preferred, but tumor tissue from diagnosis if obtained prior to neoadjuvant chemotherapy is acceptable if no relapse/progression sample available.Note that this requirement may be reduced to 15 total slides for patients who have already had RNA sequencing performed on their tumor material. * Informed consent for participation for adult participants or parental permission for minor participants (with assent as appropriate based on age of participant). Inclusion Criteria for Retrospective Cohort * Age 0 - 30 years at time of initial diagnosis of the solid or CNS tumor * Diagnosis of relapsed or refractory solid or CNS tumor, without a limit on the number of prior episodes of relapse. Refractory disease is defined as disease that progresses on standard-of-care upfront therapy or requires salvage therapy due to inadequate response, e.g. bridging chemoimmunotherapy in a patient with high-risk neuroblastoma and poor end-induction response (PEIR). * Available specimens Tissue block or unstained slides available expected to yield a minimum of 15 total slides OR other specimens expected to result in adequate IHC testing may substitute for tissue above with the approval of the PI or study staff approval designee prior to submission.. Tumor tissue from relapse/progression is preferred, but tumor tissue from diagnosis if obtained prior to neoadjuvant chemotherapy is acceptable if no relapse/progression sample available. * Prior receipt of an antibody-drug conjugate (ADC). The ADC may have been received via either commercial supply or as a participant on a clinical trial. The ADC may have been received at any time during a patient's treatment course for relapsed or refractory disease and on or after January 1st, 2011 up to the time of enrollment of the final prospective participant.