Pheochromocytomas are neuro‐endocrine tumors that arise from the neural crest
derived adrenal medullary chromaffin cells, and produce catecholamines. The first
description of a patient with pheochromocytomas was done by Fränkel in 1886, but
the term pheochromocytoma was invented by the pathologists Ludwig Pick in 1912,
after the Greek words phaios, meaning dark or dusky, and chroma, meaning color,
which refers to the dark discoloration of the tumor cells in the chromium‐salt reaction.
During embryonic development, cells of the neural crest migrate along preprogrammed
pathways, and differentiate into a variety of cell types, such as the intraadrenal
and extra‐adrenal chromaffin cells, and the autonomic ganglion cells. The
adrenal medulla is composed of chromaffin cells, which are arranged in clusters,
enclosed by sustentacular cells and a stromal network. Apart from these
structures, the medulla is highly vascularized, and this is also seen in
pheochromocytomas. In general, chromaffin cells are thought to store either adrenalin
or noradrenalin, but cells containing both catecholamines have been reported in mice.
Pheochromocytomas can produce dopamine, adrenalin, noradrenalin, or a
combination, depending on their genetic background. Catecholamine production
results in sustained, labile or paroxysmal hypertension, and if patients are not treated
appropriately, pheochromocytomas will almost always cause fatal cardiovascular
events or other devastating complications.
Pheochromocytomas occur in approximately 1 or 2 per 100,000 adults in the USA per
year (0.001‐0.002%), but the exact incidence is not precisely known. The true incidence
of pheochromocytomas is probably higher (towards 0.05%) as one in twenty cases of
the incidentally‐found adrenal masses during autopsy, magnetic resonance imaging
(MRI), computed tomography (CT), or abdominal ultrasonography, is a
pheochromocytoma.
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