POU1F1 and neoplasm: Immunohistochemistry analyses identified that PIT1 cell lineage marker dominates in four PitNETs, gonadotroph PitNET marker NR5A1 (SF1) is the most abundant in five tumours and corticotroph cell lineage marker TBX19 (TPIT) has highest expression in one PitNET (Fig 1 and S1 File).