A pituitary tumor is an abnormal mass in the pituitary gland (the primary hormone-producing gland located at the base of the brain, directly above the soft palate). Benign pituitary adenomas are the most common pituitary tumor. Microadenomas are less than 1 cm, and macroadenomas are larger than 1 cm. Macroadenomas cause more severe findings since they increase pressure on the surrounding areas, particularly on the optic nerve. Malignant pituitary carcinomas rarely develop. Pituitary germinomas are rare; affected males may have gynecomastia. Craniopharyngiomas arise from the remnants of Rathke pouch and occur more commonly in children and young adults. Rathke pouch may develop into benign cysts, which may be symptomatic. Metastatic tumors to the pituitary gland are rare but have been reported.

Endocrine disorders such as hyperprolactinemia commonly occur, producing symptoms such as galactorrhea, menstrual changes, infertility, and sexual dysfunction. Other common presenting symptoms include headaches and visual changes (bitemporal visual field deficit, blurry vision, and/or diplopia). Many affected patients remain asymptomatic, and tumors are found on imaging obtained for other reasons.

A rare complication of untreated pituitary adenomas is pituitary apoplexy.