POU1F1 and growth hormone secreting pituitary adenoma 1: To compare expressions of MSH6/2 and PD-L1 mRNA by histological subtype of NFPAs, we divided 73 NFPAs into GA (SF1 lineage), SCA (TPIT lineage), NCA, and others (PIT1 lineage) including silent somatotroph adenoma, silent lactotroph adenoma, silent thyrotroph adenoma, and PIT1-positive plurihormonal adenoma, according to the 2017 WHO classification [21,22,23].