A 35-year-old woman complains of nipple discharge and irregular menses of 5 months duration. Physical examination reveals a milky discharge from both nipples. MRI shows an enlargement of the anterior pituitary. Which of the following is the most likely histologic diagnosis of this patient's pituitary tumor?

Benign tumors arising from a glandular epithelium are termed adenomas. Patients with a prolactin-secreting pituitary adenoma present with amenorrhea and galactorrhea Ectopic islands of normal tissue are called choristomas (choice B) Localized, disordered differentiation during development results in a hamaoma (choice C). Papillomas do not occur in the pituitary (choice D).