CHROMOPHOBE ADENOMA

common form of pituitary tumour and the most common cause of enlargement of the sella turcica, the bone "cavity" that houses the pituitary gland. Only rarely are chromophobe adenomas true cancers, and calcium deposits occur in only about 6 percent of the cases. Enlargement of the pituitary fossa may also occur, however, due to extra-pituitary tumours in the brain, Hodgkin's disease, or extensions from cancer elsewhere in the body. It may also become enlarged during pregnancy, in myxedema or cretinism, by dilation of a nearby artery following a localized hemorrhage, or as a result of increases in intracranial pressure. With appropriate staining techniques, such chromophobe tumours often prove to consist of amphophils-cells that are capable of secretory activity. Inappropriately high amounts of vasopressin may also occur in the plasma and urine of individuals with a chromophobe adenoma, perhaps because the tumour is secreting this polypeptide or because somehow the rate of its production is increased by the hypothalamus. The operative mortality with surgical removal of a chromophobe adenoma ranges between 5 and 15 percent. The appearance of sudden blindness, however, in a person with a chromophobe adenoma is an indication that a hemorrhage has occurred in the tumour and is a signal for instant surgery if vision is to be restored. The relative ineffectiveness of irradiation in the treatment of chromophobe pituitary adenomas in the past has been partially canceled by the use of higher voltages directed more precisely at the tumour. Though results with X-ray irradiation of the adenoma may equal those seen following surgical removal, better results may be obtained by combining the two forms of therapy.