14 cases of pituitary tumors have been described in the literature, four nonfunctioning (9, 40), five with acromegaly (11, 39, 41, 42), five with Cushing’s disease (9, 22, 38), and the first described case of a prolactinoma resulting from a pathogenic CDKN1B mutation has now been identified in this series. Here, CDKN1B is linked to acromegaly.