Study of Nivolumab and Ipilimumab in Children and Young Adults With INI1-Negative Cancers

Inclusion Criteria: * All participants must have one of the following histologically confirmed tumors at original diagnosis or relapse: * Stratum 1 * Malignant rhabdoid tumor (MRT) * Rhabdoid tumor of the kidney (RTK) * Epithelioid sarcoma * Chordoma (poorly differentiated or de-differentiated) * Other INI1-negative or SMARCA4-deficient malignant tumors (with PI approval) * Stratum 2 * Atypical teratoid rhabdoid tumor (ATRT) * Other INI1-negative or SMARCA4-deficient primary CNS malignant tumors (with PI approval) * All participants must have tumor assessment at original diagnosis or relapse showing the following: * Loss of INI1 confirmed by immunohistochemistry (IHC), OR * Molecular confirmation of tumor bi-allelic SMARCB1 (INI1) loss or mutation when INI1 IHC is equivocal or unavailable * Loss of SMARCA4 confirmed by IHC or molecular confirmation of tumor bi-allelic SMARCA4 loss or mutation when SMARCA4 is equivocal or unavailable * Relapsed or refractory disease and no standard treatment options as determined by locally or regionally available standards of care and treating physician's discretion * Measurable disease as defined by RECIST v1.1 (Stratum 1) or RANO criteria (Stratum 2) * Karnofsky performance status ≥ 50% for participants ≥16 years of age and Lansky performance status ≥ 50% for participants \<16 years of age * Participants must have fully recovered from the acute toxic effects of all prior anti-cancer therapy. Partic…