Histological changes and operative findings of pituitary adenomas after bromocriptine treatment

Abstract

Twenty-eight patients with various types of pituitary adenomas were studied endocrinologically and neuroradiologically. We observed the changes of tumor size during bromocriptine treatment. After various periods of bromocriptine therapy, we operated on these tumors and examined then histologically. One of 5 patients with nonfunctioning adenomas improved remarkably in his visual field and acuity after 7-month bromocriptine therapy. The pathological findings disclosed remarkable changes in tumors composed of shrunken island-like cell nests and acellular spaces. These shrunken island-like cell nests were composed of tumor cells whose cytoplasmic volume decreased and whose nuclear chromatin clumped. In acellular spaces, there were irreversibly destructed tumor cells, hyaline substances, tumor cell debris and collagen fibrils. One of 8 cases of acromegalies showed a remarkably reduced tumor on CT with clinical improvement after treatment with bromocriptine for 10 months. This patient's serum growth hormone titer was raised by an abnormal response to intravenously injected TRH (thyrotropin releasing hormone), and his serum prolactin was abnormally high. Therefore, this tumor was thought to be a mixed adenoma with growth hormone secreting and/or prolactin secreting cells. Histological examinations disclosed cell shrinkage of tumor cells. Interestingly, there were scanty fibrotic changes in this tumor in spite of the long term bromocriptine therapy. In 15 cases of prolactinomas, the larger the tumor size and the longer the period of the bromocriptine therapy, the more fibrosis was seen. Under a period of bromocriptine therapy longer than 3 months, the fibrotic changes of tumor progressed, and this made more difficulty in selective adenomectomy even in the case of intrasellar adenomas. Therefore we thought that transsphenoidal surgery could successfully be done within 3 months during continuation of bromocriptine therapy.