Pituitary adenoma classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ahmad Al Maradni, M.D. [2]

Overview

Pituitary adenoma may be classified according to the size of the adenoma and type of hormone secretion, subtypes include corticotrophic, somatotrophic, thyrotrophic, gonadotrophic, and lactrotrophic adenomas.

Classification

• Historically, pituitary tumors were classified as basophilic, acidophilic, or chromophobic based on the positivity of hematoxylin and eosin stain.
• Newer classification is based on either the size or the functional status of the adenoma (secretory vs. non-secretory).

Classification based on hormone secretion and immunohistochemical staining

Type of adenoma	Secretion	Staining	Pathology
Corticotrophic adenomas	Adrenocorticotropic hormone (ACTH) and pro-opiomelanocortin (POMC)	Basophilic	Cushing's disease
Somatotrophic adenomas	Growth hormone (GH)	Acidophilic	Acromegaly (gigantism)
Thyrotrophic adenomas (rare)	Thyroid-stimulating hormone (TSH)	Basophilic	Occasionally hyperthyroidism/Asymptomatic
Gonadotrophic adenomas	Luteinizing hormone (LH), follicle-stimulating hormone (FSH) and their subunits	Basophilic	Asymptomatic
Lactrotrophic adenomas or prolactinomas (most common)	Prolactin	Acidophilic	Galactorrhea, hypogonadism, amenorrhea, infertility, and impotence
Null cell adenomas	Do not secrete hormones	May stain positive for synaptophysin

Classification based on the size of the adenoma

Pituitary adenoma may be classified into 4 grades based on radioanatomical:

• Stage I involves microadenomas (<1 cm) without sella expansion
• Stage II involves macroadenomas (≥1 cm) and may extend above the sella
• Stage III involves macroadenomas with enlargement and invasion of the floor or suprasellar extension
• Stage IV involves macroadenomas that cause destruction of the sella