are rare tumors of the adrenal glands, which are located right above the kidneys. Although they are usually not cancerous (benign), pheochromocytomas often cause the adrenal glands to make too many stress hormones called epinephrines and norepinephrines. This can lead to high blood pressure and cause symptoms such as severe headaches, irritability, sweating, rapid heart rate, nausea, vomiting, weight loss, weakness, chest pain, and a feeling of anxiety. Rarely, this kind of tumor occurs outside the adrenal gland, usually somewhere in the abdomen, and are called extra-adrenal pheochromocytomas or paragangliomas. Pheochromocytomas can occur in certain familial genetic syndromes. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.