Pituitary Adenoma

Benign tumour derived from cells of anterior pituitary

Aetiology

  • Sporadic or associated with MEN1

Pathophysiology

Micro-adenomas

  • Adenomas <1cm
  • Much less aggressive than macroadenomas

Macroadenomas

  • Adenomas >1cm
  • Can present with visual field defects due to compression of the optic chiasma
  • Can cause pressure atrophy of normal surrounding cell tissue
  • Infarction can lead to panhypopituitarism

Aggressive lesions

  • A subset of adenomas behave aggressively and enlarge more rapidly (but don't metastasise as still benign)
  • Features which indicate an agressive lesion include lots of mitotic figures and p53 mutations

Pituitary carcinoma

  • Rare, account for <1% of pituitary tumours
  • Often functional (prolactin or ACTH usually)
  • Metastasise late after multiple recurrences

Clinical presentation

Non-functioning adenomas

  • Present due to mass effects

Functioning adenomas

Functioning pituitary adenomas are classified by cell type/hormone produced:
  • Prolactin (20-30%) - most common functional tumour
  • FSH/LH (10-15%)
  • GH (5%) → gigantism (children) or acromegaly (adults)
  • ACTH - usually a microadenoma, → Cushing's, bilateral adrenocortical hyperplasia
  • Can produce more than one hormone
  • Hormone production may be at subclinical levels

Investigations

Prolactinoma

  • Serum prolactin raised
  • MRI pituitary
    • Micro vs macro
    • Involvement of pituitary stalk/optic chiasma
  • Visual fields - bitemporal hemianopia
  • Other pituitary hormone tests to assess whether other hormones are being affected

Management

  • Transphenoidal surgery
  • Replace hormones