Extra-adrenal paraganglioma: presentation in three uncommon locations.

Extra-adrenal paragangliomata are uncommon entities. They can be classified into four basic groups according to their anatomical sites, i.e. branchiomeric, intravagal, aorticosympathetic and visceral autonomic. Similar tumours may arise in sites away from the usual distribution of the sympathetic and parasympathetic ganglia, e.g. orbit, nose, small intestine and even in the pancreas. We report three instructive cases of extra-adrenal paraganglioma which were found in unusual sites such as urinary bladder, thyroid gland and on the wall of the inferior vena cava.