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
Pituitary tumors were, historically, classified as basophilic, acidophilic, or chromophobic on the basis of whether or not they took up the stains hematoxylin and eosin. This classification has fallen into disuse, in favor of a classification based on what type of hormone is secreted by the tumor (though tumors, which do not secrete any active hormone ("non-functioning tumors") are still sometimes called "chromophobic"). At present, classification of pituitary tumors is based on size, plasma hormone levels, or immunohistochemical staining.
Classification based on hormone secretion and immunohistochemical staining
| Type of adenoma | Secretion | Staining | Pathology |
| Corticotrophic adenomas | secrete adrenocorticotropic hormone (ACTH) and pro-opiomelanocortin (POMC) | basophilic | Cushing's disease |
| Somatotrophic adenomas | secrete growth hormone (GH) | acidophilic | acromegaly (gigantism) |
| Thyrotrophic adenomas (rare) | secrete thyroid-stimulating hormone (TSH) | basophilic | occasionally hyperthyroidism, usually doesn't cause symptoms |
| Gonadotrophic adenomas | secrete luteinizing hormone (LH), follicle-stimulating hormone (FSH) and their subunits | basophilic | usually doesn't cause symptoms |
| Lactrotrophic adenomas or prolactinomas (most common) | secrete 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
The radioanatomical classification places adenomas into 1 of 4 stages:
- Stage I are microadenomas (<1 cm) without sella expansion
- Stage II are macroadenomas (≥1 cm) and may extend above the sella
- Stage III are macroadenomas with enlargement and invasion of the floor or suprasellar extension
- Stage IV are macroadenomas that cause destruction of the sella