Limited reports of brain pathology in patients with irEncephalitis show perivascular CD8+ lymphocytic infiltrate.43,44 Notably, histopathological findings of pseudoprogression in the brain related to ICI treatment are similar.37 While biopsy cannot distinguish between irEncephalitis and pseudoprogression, the presence of lymphocytic infiltrate in the absence of tumor cells makes tumor progression unlikely. The gene discussed is CD8A; the disease is neoplasm.