Pheochromocytoma
A pheochromocytoma is a tumor that usually originates from the adrenal glands' chromaffin cells, causing overproduction of catecholamines, powerful hormones that induce high blood pressure and other symptoms.
Pheochromocytomas may grow within the adrenal glands or in chromaffin cells outside the adrenal glands. Only 5% of pheochromocytomas that grow within the adrenal glands are cancerous, but this percentage is higher for those outside the adrenal glands. Pheochromocytomas may occur in men or women at any age, but they are most common in people between the ages of 30 and 60.
Some people who develop pheochromocytomas have a rare inherited condition, called multiple endocrine neoplasia, that makes them prone to tumors in the thyroid, parathyroid, and adrenal glands (see Section 13, Chapter 167). Pheochromocytomas may also develop in people who have von Hippel-Lindau disease and in those who have neurofibromatosis (von Recklinghausen's disease).
Symptoms
Pheochromocytomas are usually very small. However, even a small pheochromocytoma can produce large amounts of potent catecholamines. Catecholamines are hormones such as adrenaline (epinephrine), norepinephrine, and dopamine, which tend to greatly increase blood pressure, heart rate, and other symptoms usually associated with life-threatening situations.
The most prominent symptom of a pheochromocytoma is high blood pressure, which may be very severe. Other symptoms include a fast and pounding heart rate, excessive sweating, light-headedness when standing, rapid breathing, cold and clammy skin, severe headaches, chest and stomach pain, nausea, vomiting, visual disturbances, tingling fingers, constipation, and an odd sense of impending doom. When these symptoms appear suddenly and forcefully, they can feel like a panic attack. In half of the people, symptoms come and go, sometimes triggered by pressure on the tumor, massage, drugs (especially anesthesia and beta-blocking drugs), emotional trauma, and, on rare occasions, the simple act of urination. However, many people may have these symptoms as manifestations of an anxiety state, not a glandular disorder.
Diagnosis
A doctor may not suspect a pheochromocytoma, because almost half of the people have no symptoms other than persistent high blood pressure. However, when high blood pressure occurs in a young person, comes and goes, or accompanies other symptoms of pheochromocytoma, the doctor may request certain laboratory tests. For example, the level of certain catecholamines may be measured in blood or urine samples. Because of high blood pressure and other symptoms, a doctor may prescribe a beta-blocker before knowing that the cause is a pheochromocytoma. Beta-blockers can make high blood pressure worse in people with pheochromocytoma. This paradoxical reaction often makes the diagnosis of pheochromocytoma clear.
If the level of catecholamines is high, a computed tomography (CT) or magnetic resonance imaging (MRI) scan can help locate the pheochromocytoma. A test using injected radioactive chemicals that tend to accumulate in pheochromocytomas is also useful. A scan is then performed to see where the radioactive chemicals are.
Treatment
Usually the best treatment is to remove the pheochromocytoma. Surgery is often delayed, however, until a doctor can bring the tumor's secretion of catecholamines under control with drugs, because having high levels of catecholamines can be dangerous during surgery. Phenoxybenzamine is generally given to stop hormone secretion. Once this step is accomplished, a beta-blocker can safely be given to further control symptoms.
If the pheochromocytoma is cancerous and has spread, chemotherapy with cyclophosphamide, vincristine, and dacarbazine may help slow the tumor's growth. Treatment with a radioisotope known as MIBG that targets the tumor tissue can also be highly effective. The dangerous effects of the excess catecholamines secreted by the tumor can almost always be blocked by continuing to take phenoxybenzamine or a similar drug and beta-blockers.
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