This phase III trial compares the effects of nivolumab with chemo-immunotherapy versus chemo-immunotherapy alone in treating patients with newly diagnosed primary mediastinal B-cell lymphoma (PMBCL). Immunotherapy with monoclonal antibodies, such as nivolumab, may help the body's immune system attack the cancer, and may interfere with the ability of cancer cells to grow and spread. Treatment for PMBCL involves chemotherapy combined with an immunotherapy called rituximab. Chemotherapy drugs work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Rituximab is a monoclonal antibody. It binds to a protein called CD20, which is found on B cells (a type of white blood cell) and some types of cancer cells. This may help the immune system kill cancer cells. Giving nivolumab with chemo-immunotherapy may help treat patients with PMBCL.

This phase II/III trial studies how well sentinel lymph node biopsy works and compares sentinel lymph node biopsy surgery to standard neck dissection as part of the treatment for early-stage oral cavity cancer. Sentinel lymph node biopsy surgery is a procedure that removes a smaller number of lymph nodes from your neck because it uses an imaging agent to see which lymph nodes are most likely to have cancer. Standard neck dissection, such as elective neck dissection, removes many of the lymph nodes in your neck. Using sentinel lymph node biopsy surgery may work better in treating patients with early-stage oral cavity cancer compared to standard elective neck dissection.