what is a patuitary tumor
About Pituitary Tumors. A pituitary tumor is a growth of abnormal cells in the tissues of the pituitary gland. Pituitary tumors form in the pituitary gland, a pea-sized organ in the center of the brain, just above the back of the nose. These tumors grow very slowly and do not spread from the pituitary gland to other parts of the body. 2  Invasive pituitary adenomas: Benign tumors that may spread to bones of the skull or the sinus cavity below the pituitary gland. 3  Pituitary carcinomas: Tumors that are malignant (cancer).