Endocrine surgical pathology: lesson from pituitary cases that are discordant between clinical and pathologic diagnoses.

There are a variety of clinicopathologic situations of pituitary lesions that could cause a discordance of diagnosis between clinicians and pathologists. This may be caused by confusion of terminology such as "nonfunctioning adenoma" and "null cell adenoma." "Clinically nonfunctioning pituitary adenomas" comprise several pathologically different types of tumors that belong to one of three major cell lineages of adenohypophysial cell types. "Null cell adenoma" was originally defined by ultrastructural features but recently refers to immunonegative adenomas. Unique and unusual types of adenomas such as adenomas with "honeycomb Golgi" appearance and silent subtype 3 adenomas may cause a discordance of diagnosis. Because of mild elevation of prolactin levels, these adenomas are sometimes erroneously diagnosed as prolactinoma. Careful pathologic study with immunohistochemistry and electron microscopic examination, as well as communication between clinicians and pathologists, is vital. Confusion of terminology should be discussed. Awareness of rare disease entities is also required. Thorough analysis of individual cases with diagnostic inconsistency may provide a useful lesson for better understanding of endocrine diseases and for appropriate treatments.