Definition of Pheochromocytoma:

Pheochromocytoma is a rare tumor of the adrenal gland that causes too much release of epinephrine and norepinephrine -- hormones that regulate heart rate and blood pressure.

Causes, incidence, and risk factors:

Pheochromocytoma may occur as a single tumor or as more than one growth. It usually develops in the center (medulla) of one or both adrenal glands. Sometimes this kind of tumor occurs outside the adrenal gland, usually somewhere else in the abdomen.

Less than 10% of pheochromocytomas are cancerous (malignant), meaning they have the potential to spread to other parts of the body.

The tumors may occur at any age, but they are most common from early to mid-adulthood. About 10% of the time there is a family history of the disease.