SMARCB1 and kidney medullary carcinoma: On one hand, SMARCB1-deficient tumors often exhibit low tumor mutation burden, which may render them less responsive to immunotherapy.In a phase II clinical trial that reported the first prospective study of renal medullary carcinoma (RMC) with loss of SMARCB1 protein (also known as INI-1, hSNF5, or BAF47), results showed no evidence of clinical activity of pembrolizumab in RMC patients, regardless of PD-L1 or tumor-infiltrating lymphocyte (TIL) levels (18).