Final answer:
The most common benign tumor of the pituitary gland is a prolactinoma, a non-cancerous tumor that produces excess prolactin and can often be treated with medication or surgery.
Step-by-step explanation:
The most common benign tumor of the pituitary gland is known as a prolactinoma. Prolactinomas are characterized by the overproduction of prolactin, which is a hormone produced by the anterior pituitary that promotes the development of mammary glands and the production of breast milk. Excess prolactin from the tumor can lead to various symptoms, such as galactorrhea (milky nipple discharge unrelated to normal breastfeeding) or gynecomastia in men. This type of tumor is generally not cancerous and can often be treated with medications that reduce prolactin levels or surgery if the tumor is large or causing vision problems due to its proximity to the optic chiasm.