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, historically, 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 | 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 grades:
- 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