An overview of pituitary tumors.

Tumors arising in and around the hypophyseal fossa can cause symptoms by compression of surrounding structures or, in the case of adenomas arising from the adenohypophysis, by hypersecretion of hormones. Until recently, adenomas of the hypophysis have been classified on the basis of light microscopy into chromophobe, eosinophilic and basophilic. Presently available methods of histochemistry, immunocytology, electron microscopy and hormone assays make available a biological classification of these adenomas into two groups: (I) adenomas without secretory activity and (II) adenomas with secretory activity. Amongst the latter are included somatotroph adenomas, prolactin cell adenomas, melanocorticotroph adenomas and thyrotroph adenomas. Many of the large group of tumors formerly called "chromophobe" can now be reclassified amongst the secretory adenomas.