TABLE I.

Characteristics of the two broad categories of paragangliomas (World Health Organization classification)^3–8

Characteristic	Sympathoadrenal	Parasympathetic
Chromaffin status	Chromaffin paragangliomas	Non-chromaffin paragangliomas, often called chemodectomas or glomus tumours
Location	Adrenal medulla (most common)	Head and neck, also upper mediastinum
Distribution	Also symmetrically distributed along the prevertebral and paravertebral axis (thoracoabdominal and pelvic paraganglia)	Found in 20 distinct anatomic locations: carotid body (major paraganglion, the most common tumour location), jugular foramen, Jacobsen tympanic plexus, and vagal and aortic paraganglia (upper mediastinum)
Hormonal activity	Usually, but not always, hormonally active (catecholamine producing: noradrenalin, adrenalin, dopamine, l-dopa)	Hormonally inactive in 95% of cases (only rarely associated with catecholamine production)