A benign tumor of glandular origin. There are three types of adenomas: tubular (most common, tubelike structure), villous (least common, most likely to become cancerous, ruffled structure), and tubulovillous (blend of tubular and villous structures). Adenomas do not metastasize, though they can develop into malignancies known as adenocarcinomas. Most adenomas occur spontaneously. The tumor may occur throughout the endocrine system, including the pituitary gland.
Pituitary adenomas occur at a much higher incidence in adults than in children. Because their invasiveness is local, they are almost always benign and can be difficult to detect. There is the secreting and the nonsecreting type. Clinical symptoms come from the endocrine dysfunction or from mass effect and include headaches, hypopituitarism, and visual loss (caused by compression in the optic chiasm). Treatment of pituitary adenomas includes correction of electrolyte dysfunction, replacement of pituitary hormones, surgical resection, and radiotherapy.