Tumors in the Adenohypophysis

The human pituitary gland is located in the sella turcica and consits of the adenohypophysis and the neurohypophysis. The adenohypophysis, comprising approximately 80% of the entire pituitary gland, produces six hormones, including growth hormone (GH), prolactin (PRL), and adrenocorticotropin (ACTH) – as well as the three glycoprotein hormones – thyrotropin or thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). Tumors of the pituitary gland are classified based on the five-tier cassification scheme that is now embodied in the World Health Organization classification of tumors. Clinical, endocrine, imaging, and operative as well as histological findings all contribute to the current classification of these tumors. Ultrastructural study of pituitary tumors is also important in their classification. In this chapter, we discuss morphological characteristics of pituitary tumor subtypes including GH-, PRL-, ACTH-, TSH-, FSH/LH-producing adenomas, as well as silent and null cell adenomas and pituitary carcinomas.