Pheochromocytomas are functionally active tumors arising from chromaffin cells of the adrenal medulla or in rests of chromaffin tissue, wherever it may be located. Approximately 98% of these tumors occur in the abdomen; 2%, in the neck and thorax. About 90% of the abdominal pheochromocytomas are located in the adrenal glands; the rest may be found along the abdominal aorta or its main branches at the site of paravertebral sympathetic ganglia, in the bladder wall, or along the spermatic cord.
Although they usually occur sporadically, 10% of pheochromocytomas are familial. These lesions are associated with the following neoplasias: (1) von Recklinghausen's disease (neurofibromatosis); (2) Sipple's syndrome, ie, bilateral adrenal tumors, medullary carcinoma of the thyroid, and hyperparathyroidism (multiple endocrine neoplasia [MEN type 2a]); (3) mucocutaneous neuromasa, with bilateral adrenal tumors, medullary carcinoma of the thyroid, and ganglioneuromas of the visceral anatomic plexuses (MEN type 2b); and (4) von Hippel-Lindau disease