A Study Involving Collection of Samples and Data From Sarcoma Patients Receiving Immunotherapy

Inclusion Criteria: * Participants must have a histologic diagnosis of sarcoma confirmed by an MSK pathologist. * Any prospectively identified patient being treated or to be treated with an immune checkpoint inhibitor, such as anti-PD-1, anti-PD-L1, anti-CTLA-4, or anti-LAG3 inhibitor, either as monotherapy or in combination with additional systemic therapy OR any prospectively identified patient being treated or to be treated with ACT-based treatment including but not limited to lifileucil, Afamitresgene autoleucel, and letetresgene autoleuce o Novel immune checkpoints inhibitors that are developed after submission of this protocol will also be included) Please Note: there is no age requirement. Patients of all ages are eligible to enroll Exclusion Criteria: * Patient unwilling to consent to collection of historical and longitudinal clinicopathologic data in the patient medical record from baseline (the period prior to ICB or ACT initiation), during, and after ICB or ACT treatment