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Paraganglioma

Summary

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  • Rare neuroendocrine tumours arising from extra-adrenal paraganglia
  • Typically present with symptoms related to catecholamine excess or mass effect
  • Imaging plays crucial role in diagnosis, localization, and staging

Pathophysiology

  • Derived from neural crest cells of the autonomic nervous system
  • Can be functional (secreting catecholamines) or non-functional
  • Associated with various genetic syndromes (e.g., SDHx mutations, VHL, NF1)
  • Malignant potential in 10-20% of cases

Demographics

  • Incidence: 2-8 per million person-years
  • Peak incidence: 30-50 years old
  • Slight male predominance
  • Higher prevalence in patients with genetic predisposition syndromes

Diagnosis

  • Clinical presentation:
    • Hypertension (paroxysmal or sustained)
    • Headaches, palpitations, sweating
    • Abdominal pain or mass effect symptoms
  • Biochemical testing:
    • Plasma or urinary metanephrines and catecholamines
    • Chromogranin A levels
  • Genetic testing for associated syndromes

Imaging

  • CT:
    • Contrast-enhanced CT: hypervascular, well-defined masses
    • Washout characteristics differ from adrenal adenomas
  • MRI:
    • T1: iso- to hypointense
    • T2: markedly hyperintense ("light bulb" sign)
    • Strong enhancement on post-contrast images
  • Functional imaging:
    • 123I-MIBG scintigraphy: high specificity for paragangliomas
    • 68Ga-DOTATATE PET/CT: superior sensitivity, especially for SDHx-related tumours
    • 18F-FDG PET/CT: useful for detecting metastatic disease

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  • 40-year-old patient presented with hearing loss and facial palsy.
  • MRI showed a lesion in the left jugular foramen and petromastoid bone with evidence of vascularity on T2-weighted imaging (i.e., flow voids) and time-of-flight angiography. Ga-DOTATATE PET showed avid tracer uptake as expected in a paraganglioma.

Treatment

  • Surgical resection: primary treatment modality
  • Preoperative management:
    • Alpha-adrenergic blockade (e.g., phenoxybenzamine)
    • Beta-blockers as adjunct therapy
  • Radiotherapy: for unresectable or metastatic disease
  • Systemic therapies:
    • 131I-MIBG therapy for MIBG-avid tumours
    • Peptide receptor radionuclide therapy (PRRT) for somatostatin receptor-positive tumours
    • Chemotherapy for rapidly progressive disease
  • Long-term follow-up: essential due to risk of recurrence and metastasis

Differential diagnosis

Differential Diagnosis Differentiating Feature
Pheochromocytoma Located in adrenal gland, while paragangliomas are extra-adrenal
Carotid body tumour Specifically located at carotid bifurcation, "lyre sign" on angiography
Schwannoma Typically encapsulated, heterogeneous enhancement on MRI
Metastatic lymph node Irregular borders, loss of fatty hilum on imaging
Glomus tympanicum Located in middle ear, associated with pulsatile tinnitus
Meningioma Dural tail sign on MRI, calcifications more common
Vagal paraganglioma Splays carotid bifurcation anteriorly (unlike carotid body tumour)
Aneurysm Pulsatile, shows flow on Doppler ultrasound
Neurofibroma Associated with café-au-lait spots, target sign on MRI