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Pituitary Macroadenoma

Summary

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  • Benign tumour of the pituitary gland >10mm in size
  • Presents with mass effect symptoms and/or hormonal dysfunction
  • Characterised by sellar expansion and suprasellar extension on imaging

Pathophysiology

  • Arise from adenohypophyseal cells of the anterior pituitary
  • Can be functional (hormone-secreting) or non-functional
  • Growth leads to compression of surrounding structures:
    • Optic chiasm
    • Cavernous sinus
    • Hypothalamus
  • Hormonal imbalances due to:
    • Excessive hormone production (in functional adenomas)
    • Pituitary gland compression (hypopituitarism)

Demographics

  • Peak incidence: 30-60 years of age
  • Slight female predominance (1.2:1)
  • Accounts for 10-15% of intracranial neoplasms
  • Prevalence: 1 in 1000 in the general population

Diagnosis

  • Clinical presentation:
    • Mass effect symptoms:
    • Headache
    • Visual field defects (classically bitemporal hemianopsia)
    • Cranial nerve palsies
    • Hormonal symptoms (depending on tumour functionality):
    • Prolactinoma: Galactorrhea, amenorrhea, infertility
    • Growth hormone-secreting: Acromegaly or gigantism
    • ACTH-secreting: Cushing's disease
    • TSH-secreting: Hyperthyroidism
  • Laboratory tests:
    • Serum hormone levels (prolactin, GH, IGF-1, ACTH, cortisol, TSH, free T4)
    • Dynamic endocrine testing as needed
  • Ophthalmological evaluation:
    • Visual field testing
    • Visual acuity assessment

Imaging

  • MRI (gold standard):
    • T1-weighted:
    • Isointense to gray matter
    • Hypointense to white matter
    • T2-weighted:
    • Hyperintense to gray matter
    • Contrast-enhanced T1:
    • Heterogeneous enhancement
    • Key features:
    • Sellar expansion
    • Suprasellar extension
    • Cavernous sinus invasion (if present)
  • CT:
    • Hypodense to isodense mass
    • Sellar expansion and remodeling
    • Calcifications (in 5-25% of cases)
  • Dedicated pituitary protocol:
    • Thin-slice (1-3mm) coronal and sagittal images
    • Dynamic contrast-enhanced sequences

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  • 60-year-old patient with a large heterogeneously enhancing lesion within an expanded pituitary fossa. The optic chiasm is elevated and compressed.

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  • 25-year-old patient presented with a seizure.
  • MRI showed a large, enhancing (not shown) lesion centred in the pituitary fossa but with extensive erosion of the skull base.
  • A hemtoma formed in the right lateral aspect of the lesion, the mass effect of which presumably provoked the seizure.
  • Serum prolactin was >800,000. Prolactin levels and the size of the lesion significantly reduced after starting cabergoline.
  • 60-year-old patient presented with facial changes typical of acromegaly.
  • MRI showed a 1.2 cm T2-hypointense lesion in the anterior aspect of the pituitary gland. The lesion was subtly hypoenhancing.

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  • A 25-year-old patient presented with headache and visual disturbance.
  • MRI showed a massive skull base lesion centred on the pitutary fossa with involvement of the cavernous sinuses and extension along the clivus.
  • After 1 year on cabergoline, the prolactinoma shrunk to a fraction of its original size.

Treatment

  • Management approach depends on:
    • Tumour size and extension
    • Hormonal activity
    • Patient's symptoms and comorbidities
  • Surgical resection:
    • Transsphenoidal approach (endoscopic or microscopic)
    • Goals: Decompression, hormone normalization, tissue diagnosis
  • Medical therapy:
    • Prolactinomas: Dopamine agonists (e.g., cabergoline, bromocriptine)
    • GH-secreting: Somatostatin analogs (e.g., octreotide, lanreotide)
    • ACTH-secreting: Steroidogenesis inhibitors (e.g., ketoconazole)
  • Radiation therapy:
    • Reserved for residual or recurrent tumours
    • Stereotactic radiosurgery or fractionated radiotherapy
  • Hormonal replacement:
    • For hypopituitarism due to tumour compression or treatment effects
  • Regular follow-up:
    • Serial MRI scans
    • Endocrine evaluation
    • Visual field testing

Differential diagnosis

Differential Diagnosis Differentiating Feature
Craniopharyngioma Calcifications on CT; cystic components more common
Meningioma Dural tail sign on MRI; homogeneous enhancement
Rathke's cleft cyst Lack of solid component; thin wall enhancement
Metastasis Irregular enhancement; bone destruction; posterior pituitary or infundibular predilection
Germ cell tumour Midline pineal or suprasellar location; loss of posterior pituitary bright spot; thickened infundibulum
Chordoma Destructive lesion of the clivus