POMC and oncocytic adenoma: In fact, NFPA is highly heterogeneous – it has different types of cell origins and hormones expressed in tumor tissues, including silent somatotroph (growth hormone GH-positive; 3%), silent corticotroph (adrenocorticotropic hormone ACTH-positive; 8%), oncocytoma (no hormone expression; 6%), null cell (no hormone expression; 17%), and gonadotroph (intact follicle-stimulating hormone/luteinizing hormone FSH/LH or subunits; 40-79%) that was subclassified as LH-positive, FSH-positive, and LH/FSH-positive NFPAs [15].