WHO classification recognizes five categories of pituitary adenomas that are shown to be more clinically aggressive regardless of their histological grading: sparsely granulated somatotroph adenomas, lactotroph macroadenomas in men, Crooke cell adenoma, silent corticotroph adenomas, and plurihormonal Pit-1 positive adenoma [2]. Here, POU1F1 is linked to acromegaly.