Refractory Primary Mediastinal B-Cell Lymphoma: A Case Report of Conventional Chemotherapies, Immune Checkpoint Inhibitors, Polatuzumab Vedotin, Transplantation, and Post-Transplant Large Granular Lymphocytosis

We report a case of stage IV primary mediastinal B-cell lymphoma in a 27-year-old young woman, who was refractory and chemoresistant to frontline conventional rituximab-based intensive chemotherapy and subsequent lines of conventional and immune checkpoint inhibitor-based therapies. She was successfully treated using a polatuzumab-based regimen and consolidated with an allogeneic haploidentical hematopoietic stem cell transplantation. She developed post-transplant large granular lymphocytosis that was managed conservatively. She is now relapse-free, 600 days post-transplant. The management of this patient provided several teaching points in the use of different modalities of immunotherapies in a hard-to-treat cancer and its related conditions.