Tiragolumab and Atezolizumab for the Treatment of Relapsed or Refractory SMARCB1 or SMARCA4 Deficient Tumors

Inclusion Criteria: * Patients must be \>= 12 months of age at the time of study enrollment. For part A, patients must be \< 18 years old at enrollment. For part B, there is no upper age limit * The Part B (phase 2) cohorts will initially open concurrently with the part A but will only enroll patients at least 18 years of age. Patients \< 18 years of age will be included in the part B cohorts only after the tiragolumab monotherapy dose has been assessed to be safe in the part A portion * Patients must have SMARCB1 (INI1) or SMARCA4 deficient tumors verified through institutional immunohistochemistry (IHC) or molecular confirmation of a pathologic SMARCB1 (INI1) or SMARCA4 loss or mutation in the tumor from a Clinical Laboratory Improvement Act (CLIA) certified lab with the following disease histologies: * Renal medullary carcinoma * Malignant rhabdoid tumor (extra-CNS) * Atypical teratoid rhabdoid tumor (CNS) * Poorly differentiated chordoma * Epithelioid sarcoma * Other SMARCB1 or SMARCA4 deficient tumors * Note: Molecular studies will only be used if IHC is equivocal or cannot be performed. Documentation of the institutional IHC or molecular testing must be uploaded via the RAVE system * Part A: Patients must have either measurable or evaluable disease Part B: Patients must have measurable disease per RECIST v1.1 for non-CNS tumors or CNS response criteria for CNS tumors * Note: See protocol for specific exclusion for patients with CNS primary or metas…