The purpose of this research study is to find new ways of detecting and treating Hodgkin lymphoma and primary mediastinal B-cell lymphoma (a cancer of mature B-lymphocytes). It is a form of non-Hodgkin lymphoma, a type of cancer that originates in cells of the immune system, called lymphocytes. The information we learn by doing this research study may help study doctors identify new ways of treating your type of lymphoma. Participants in this study will provide archival (stored) tissue and blood samples. Participation is expected to last about 8 months. The risks and discomforts of this study are minimal. All blood specimens requested for this study will be collected at the time of routine procedures.

This is a study for patients with relapsed/refractory large B-cell lymphoma or follicular lymphoma. Patients who have either stable disease or a partial response to CD19 CAR T-Cell therapy may be eligible. The purpose of the study is to compare groups of patients who either receive therapy after CAR T-cells and patients that do not receive further therapy after CAR T-cells.