What are the types of nonfunctioning adenomas?
Nonfunctional pituitary tumors are subtyped by immunohistochemical staining for the various pituitary hormones and the pituitary-specific transcription factors that delineate their pituitary cell lineages. NFAs constitute a heterogeneous group of tumors, including the following:
• Gonadotrophs the vast majority of cases [80%]—stain for LH-beta, FSH-beta, and/or alpha subunit and/or the transcription factor SF-1.
• Null cell tumors (negative immunoreactivity for both pituitary hormones and pituitary transcription factors).
• Silent adenomas (e.g., corticotroph adenomas—positive ACTH/T-Pit staining; somatotroph adenomas—positive GH/Pit-1 staining; or thyrotropinomas—positive thyroid-stimulating hormone [TSH]/ Pit-1 staining), but without clinical stigmata of hormone excess.
• Plurihormonal pituitary tumors (which stain for multiple pituitary hormones), although generally are not clinically evident.