Phaeochromocytoma

From Ganfyd

An endocrine tumour that should be considered in the differential diagnosis of secondary hypertension. Commonly found in the adrenal medulla.

Characteristics

Can be remembered by the remembering 90/10. About 90% are

• Benign (ie 10% malignant)
• Solitary
• In the medulla

Symptoms

Effects of catecholamine excess:

• Sweating
• Pallor
• Tachycardia/palpitations
• Agitation/anxiety
• Hypertension

Aetiology

Between 25% to 50% arise from known genetic syndromes. In these failure of developmental apoptosis may play a role in pheochromocytoma pathogenesis as Jun-B levels are increased as a common factor in most of these syndromes leading to deficits in c-Jun-dependent apoptosis during development.

• Paraganglioma syndrome type gene problems
  • Mutations in succinate dehydrogenase (SDH) genes
    • SDHB (paraganglioma syndrome type 4)
    • SDHD (paraganglioma syndromes type 1)
    • SDHC (paraganglioma syndromes type 3) - rare
• JunB-mediated apoptosis defect
• von Hippel-Lindau disease
  • Mutations in Von Hippel-Lindau (VHL) gene
• Neurofibromatosis type 1
  • Mutations in NF 1 gene
• Multiple endocrine neoplasia type 2A (MEN 2A,Sipple Syndrome)
  • Mutations in c-RET gene

Investigations

• Urinary catecholamines - commonly measured ones include adrenaline, noradrenaline, VMA and metnoradrenaline.
• MRI scanning in an attempt to localise the tumour. If this is unsuccessful then MIBG (¹²³I-metaiodobenzylguanidine) scanning can be used instead.

Treatment

Surgical removal

requires alpha and beta adrenergic blockade to prevent cardiovascular collapse during the operation. Phenoxybenzamine is used for alpha-blockade due to its long half-life. The dose needs adjustment until orthostatic hypotension develops and treatment is usually started 7-10 days prior to surgery. At the moment of removal of the tumour there is a risk of massive collapse of venous tone leading to hypotension due to relative hypovolaemia. In part this can be counteracted by the anaesthetist ensuring maximal circulating volume just prior to this.