Pheochromocytoma

In pheochromocytoma, pheo- means dark, chromo- refers to color, cyto- refers to a cell and -oma means tumor. So a pheochromocytoma is a rare adrenal gland tumor where the cells darken when they form tumors.

Now, there are two adrenal glands, one above each kidney, and each one has an outer layer called the cortex and an inner layer called the medulla.

In the medulla, there are cells called chromaffin cells and their job is to make hormones called catecholamines. The catecholamines include epinephrine and norepinephrine - the fight or flight hormones.

Normally, the chromaffin cells in the adrenal gland secrete epinephrine and norepinephrine into the blood when something scary happens - like someone saying BOOM!

The epinephrine and norepinephrine bind to alpha and beta receptors in various tissues throughout our body and cause an increase in cardiac output, increased blood pressure, dilated pupils, increased blood flow to skeletal muscles, and increased blood sugar.

Pheochromocytomas are tumors that form when these chromaffin cells start to divide uncontrollably.

They typically form in one of the adrenal glands, but rarely can be in both and sometimes can even develop in other parts of the body where chromaffin cells are found like the carotid arteries in the neck, the bladder, and the abdominal aorta.

Most pheochromocytomas arise sporadically, but some are associated with an inherited syndrome.

One of these is multiple endocrine neoplasias type 2A and type 2B, where pheochromocytoma is caused by a mutation in the RET gene, which is a protooncogene that encodes for proteins that promote cell growth and division.