Invasive Pituitary Adenoma and Pituitary Carcinoma

Pituitary adenomas comprise approx 10% of all intracranial tumors. Taking their origin in the anterior lobe, most grow in a slow, expansible manner and are composed of cytologically benign cells resembling those of the normal adenohypophysis. Fully 75% are endocrinologicaly functional, secreting growth hormone (GH), prolactin (PRL), adrenocorticotropic hormone (ACTH), or thyroid-stimulating hormone (TSH), either alone or in various combination. The remainder are functionally “silent,” producing either luteinizing hormone (LH)/follicle-stimulating hormone (FSH) and/or α-subunit, or no immunostainable hormones at all. Conventional adenoma variants and their pathobiologic characteristics are fully discussed in Chapter 7.