CTLA4 and neoplasm: Immune checkpoint inhibitors (ICIs), including anti‐cytotoxic T‐lymphocyte antigen‐4 (CTLA‐4), anti‐programmed cell death 1 (PD‐1), and anti‐programmed death 1 ligand 1 (PD‐L1), have become a mainstay of treatment for many types of cancers.1 As a consequence of the favorable response rates and the improved survival provided by ICIs, these agents continue to undergo extensive evaluation for the treatment of additional tumor types, thus expanding the number of patients exposed to ICIs.2