13 October 2011 (Thursday) - Phaeochromocytoma

A phaeochromocytoma is a rare neuroendocrine tumor of the medulla of the adrenal glands (originating in the chromaffin cells), or extra-adrenal chromaffin tissue that failed to involute after birth and secretes excessive amounts of catecholamines, usually noradrenaline and adrenaline (to a lesser extent).

Extra-adrenal paragangliomas (often described as extra-adrenal pheochromocytomas) are closely related (though less common) tumors that originate in the ganglia of the sympathetic nervous system and are named based upon the primary anatomical site of origin.

The aorticosympathetic group of the adult paraganglia (derived from the embryonic organ of Zuckerkandl) is often a source of paragangliomas.

The signs and symptoms of a pheochromocytoma are those of sympathetic nervous system hyperactivity, including:

• Skin sensations
• Flank pain
• Elevated heart rate
• Elevated blood pressure, including paroxysmal (sporadic, episodic) high blood pressure, which sometimes can be more difficult to detect; another clue to the presence of pheochromocytoma is orthostatic hypotension (a fall in systolic blood pressure greater than 20 mmHg or a fall in diastolic blood pressure greater than 10 mmHg upon standing)
• Palpitations
• Anxiety often resembling that of a panic attack
• Diaphoresis (excessive sweating)
• Headaches
• Pallor
• Weight loss
• Localized amyloid deposits found microscopically
• Elevated blood glucose level (due primarily to catecholamine stimulation of lipolysis (breakdown of stored fat) leading to high levels of free fatty acids and the subsequent inhibition of glucose uptake by muscle cells. Further, stimulation of beta-adrenergic receptors leads to glycogenolysis and gluconeogenesis and thus elevation of blood glucose levels).

 A pheochromocytoma can also cause resistant arterial hypertension. A pheochromocytoma can be acutely fatal if it causes malignant hypertension, or severely high blood pressure. This hypertension is not well controlled with standard blood pressure medications.

Not all patients experience all of the signs and symptoms listed. The most common presentation is headache, excessive sweating, and increased heart rate, with the attack subsiding in less than one hour. Excessive vomitting triggered by an attack will cause compression of the tumour, and therefore release of more hormones, and so exasperating symptoms. It is for this reason that palpitating phaeochromocytomas is not advised.

Tumors may grow very large according to the literature, but nearly all are smaller than 10 cm, most being grape-sized (or smaller)