Necrotic changes in prolactinomas after long term administration of bromocriptine.

Six prolactinoma patients were studied endocrinologically and their tumors were examined histologically after long term bromocriptine therapy. In patient 1 with a large prolactinoma, a marked reduction in size and a remarkable decrease in elevated serum PRL levels occurred after bromocriptine treatment for 8 months. The histological findings consisted of two components, i.e. shrunken island-like cell nests and acellular spaces. Some degenerative and necrotic tumor cells, hyaline substance, and fibrosis were observed with light and electron microscopy in these acellular spaces. Island-like cell nests consisted of atrophic cells having disproportionally scanty cytoplasm. The same histological findings were observed in four other patients. However, in another patient whose tumor decreased in size only slightly during bromocriptine therapy, the specimen had few acellular spaces. Thus, long term bromocriptine treatment of patients with prolactinomas may result in necrosis of some adenoma cells in some patients.