Nivolumab in Combination With Chemo-Immunotherapy for the Treatment of Newly Diagnosed Primary Mediastinal B-Cell Lymphoma

Inclusion Criteria: * Age \>= 2 years * Patient must have histologically confirmed primary mediastinal B-cell lymphoma (PMBCL) as defined by World Health Organization (WHO) criteria * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 or ECOG performance status of 3 if poor performance is related to lymphoma * Children's Oncology Group (COG) Institutions: Use Karnofsky for patients \>= 17 and \< 18 years of age and Lansky for patients \< 17 years of age * Adults (age 18 or older): Creatinine clearance \>= 30 mL/min, as estimated by the Cockcroft and Gault formula. The creatinine value used in the calculation must have been obtained within 28 days prior to registration. Estimated creatinine clearance is based on actual body weight * Pediatric Patients (age \< 18 years): The following must have been obtained within 14 days prior to registration: * Measured or calculated (based on institutional standard) creatinine clearance or radioisotope glomerular filtration rate (GFR) \>= 70 ml/min/1.73 m\^2, or * Serum creatinine =\< 1.5 x institutional upper limit of normal (IULN), or a serum creatinine based on age/sex as follows: * Age : 2 to \< 6 year; Maximum serum creatinine (mg/dL): 0.8 (male; 0.8 (female) * Age : 6 to \< 10 years; Maximum serum creatinine (mg/dL): 1 (male); 1 (female) * Age : 10 to \< 13 years; Maximum serum creatinine (mg/dL): 1.2 (male); 1.2 (female) * Age : 13 to \< 16 years; Maximum serum creatinine (mg/dL): 1.5…