Accordingly, tumours with POU class 1 homeobox 1 (Pit-1)-positivity with IHC staining for growth hormone (GH), prolactin (PRL), or thyroid stimulating hormone (TSH) were classified as somatotroph tumours, lactrotroph tumours, or thyrotroph tumours, respectively. This evidence concerns the gene POU1F1 and neoplasm.