Abnormal growth and division of cells in the pituitary gland result in a pituitary tumor. Fortunately, most pituitary gland tumors are benign and do not have the potential to spread to other body parts. However, patients with pituitary tumor experience symptoms due to overproduction (functional adenomas) and underproduction of the pituitary hormones (non-functional adenomas) that control several important functions. Pituitary carcinomas are cancers of the pituitary gland and may spread to other body organs.