Optimizing ctDNA-based MRD Assessment in DLBCL, MCL, and FL Patients Undergoing CAR Therapy

Inclusion Criteria: * Immunophenotypically confirmed diagnosis of follicular lymphoma (FL), Immunophenotypically confirmed diagnosis of Large B Cell Lymphoma (LBCL) (including transformed FL and Primary Mediastinal B-cell Lymphoma) OR Immunophenotypically confirmed diagnosis of mantle cell lymphoma (MCL) undergoing commercially approved CAR-T therapy in accordance with FDA indication with enrollment in this trial prior to CAR infusion * CAR-T product must meet manufacturer specifications * PET measurable disease at the time a decision is made to prescribe CAR treatment * Has sample from diagnosis or relapse available for genomic DNA extraction to identify patient's clonotype via clonoSEQ (see lab manual for details) Exclusion Criteria: * Lack of archival diagnostic or fresh/archival relapse tissue for purposes of determining patient's lymphoma clonotype. Given that 5-10% of patients cannot have a clonotype identified by clonoSEQ, those patients will be removed from the study and excluded from analysis, but their samples will continued to be stored for future analysis as improvements to the analysis platform are made. * No patients are to be excluded on the basis of gender, race, ethnic background, sexual orientation, or other demographic characteristics.