Adrenal Medulla

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  • Developmentally distinct from the adrenal cortex
  • Composed of neural crest cells called chromaffin cells which synthesise and secrete catecholamines in response to preganglionic nerve fibres in the sympathetic nervous system

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  • The most important pathology of the adrenal medulla are neoplasms which include neoplasms of the chromaffin cells (phaeochromocytoma) and neuronal neoplasms

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Phaeochromocytoma

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  • Synthesize and release catecholamines and in some cases peptide hormones
  • Give rise to surgically correctable forms of hypertension
  • Subscribe to a ‘rule of tens’
    • 10% of phaeochromocytomas arise in association with one of several familial syndromes. These include;
      • MEN-2A and MEN-2B syndromes
      • Type I neurofibromatosis
      • Von Hippel-Lindau syndrome
      • Sturge-Weber syndrome (associated with haemangiomas of the V cranial nerve distribution)
    • 10% are extra-adrenal occurring in sites such as the organ of Zuckerkandl (close to the aortic bifurcation) and the carotid body. They are called paragangliomas
    • 10% of non-familial adrenal phaeochromocytomas are bilateral (may be 70% in familial syndromes)
    • 10% are malignant (more common in tumours arising from extra-adrenal sites)
    • 10% arise in childhood, usually related to the familial subtypes with a male preponderance (non-familial cases generally arise in middle age in women)

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Morphology

  • Can be small or large, if large are often haemorrhagic, necrotic with cystic change
  • Stain with potassium dichromate as the contain catecholamines
  • Usually tumours are very vascular
  • Miscroscopically the tumour consist of polygonal chromaffin cells clustered with sustentacular cells into small nests of alveoli (zellballen) by a rich vascular network
  • There is no single histological feature which can reliably predict the clinical behavior of phaeochromocytomas. The definitive diagnosis of malignancy is based on presence of metastases
  • Metastases generally involve the regional lymph nodes, lung, liver and bone
  • Aggressive behavior of the carcinoma is associated with;
    • Increased number of mitoses
    • Necrosis
    • Spindle cell morphology

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Clinical course

  • Dominant feature is hypertension
  • Associated with tachycardia, palpitations, headache, tremor, sweating and a sense of apprehension
  • In most patients the hypertension is chronic but there may be some paroxysmal episodes associated with stress, exercise, changes in posture
  • Cardiac complications occur called catecholamine cardiomyopathy
  • Some phaeochromocytomas can produce other hormones such as ACTH and somatostatin which may be associated with clinical features

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Neuroblastoma

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  • The most common extracranial solid tumour of childhood – occur most commonly in the first 5 years of life
  • Can occur anywhere in the sympathetic nervous system and occasionally in the brain but are most common in the abdomen arising either in the adrenal medulla or the retroperitoneal sympathetic ganglia

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