Table 1.

Classification of pituitary adenomas

Cell tvDe Adenoma Type	Population Prevalence ftotal/lO5)	Tumor transcription factor expression	Unregulated differentiated gene expression	Clinical features
Lactotroph Sparsely or densely granulated	45–50	Pit-1	Prolactin	Hypogonadism and/or galactorhea
Gonadotroph	15–20	SF-l,GATA-2	FSH and/or LH and/or glycoprotein subunit. (depending on type, null or oncocytic)	Silent or pituitary failure Ovarian hyperstimulation (reproductive age women) Testicular enlargement (prepubertal)
Somatotroph	10	Pit-1
Sparsely granulated			GH	Acromegaly or gigantism
Densely granulated			GH	Acromegaly
Combined GH and			GHand	Acromegaly or
PRL cells			prolactin	gigantism
Mixed GH and			GHand	Hypogonadism and
PRL			prolactin GH and	acromegaly Acromegaly or
Mammos omatotroph			prolactin	gigantism
Acidophil Stem			Prolactin and	Hypogonadism and
Cell			GH	acromegaly
Silent			GH	Hypopituitarism
Corticotroph	5	T-Pit	ACTH
Cushing				Cushing Disease
Silent				Hypopituitarism
Nelson				Pituitary hyperplasia
Thyrotroph	<1	Pit-1	TSH	Hyperthyroidism
Plurihormonal	Unknown	All	GH, prolactin, ACTH, glycoprotein	Mixed

All tumor types exhibit features of a pituitary mass, visible on MRI. Glycoprotein refers to intact FSH or LH, or respective α or β glycoprotein subunits. Although null-cell tumors do not express hormone genes, they are classified as gonadotroph in origin.

Abbreviations: ACTH, adrenocorticotropic hormone; FSH, follicle-stimulating hormone; GATA2, endothelial transcription factor GATA-2; GH, growth hormone; LH, luteinizing hormone; PIT1, pituitary-specific positive transcription factor 1; STF1, steroidogenic factor 1; TBX19, T-box transcription factor TBX19 (also known as TPIT).

From Melmed S 2011 Pathogenesis of pituitary tumors. Nat Rev Endocrinol 7:257-266, with permission.