Current pathological classification of pituitary adenomas.

A classification of pituitary adenomas basing on detailed structural and immunohistochemical studies is accepted world-wide and is mandatory for each pathologist. Monohormonal (densely or sparsely granulated GH cell adenomas, Prolactin cell adenomas, ACTH cell adenomas. FSH/LH cell adenomas, alpha-subunit-only adenomas), bihormonal (mixed GH/Prolactin cell adenomas, mammosomatotroph cell adenomas, acidophil stem cell adenomas), plurihormonal (GH/Prolactin/Glycoprotein-positive adenomas, other Glycoprotein-positive types) and hormone-negative adenomas (null cell adenomas, oncocytic adenomas) have to be differentiated.