Pheochromocytomas are relatively rare tumors arising from chromaffin tissue. They are reported as occurring in one of each thousand autopsies.1 Of this number, not all are symptomatic during life.
Certain statistical data are available in the literature. Huebner and Reed refer to them as "10% tumors" since approximately 10% are malignant, 10% are extra-adrenal, and 10% are bilateral or multiple.2 They occur most commonly in the fourth to sixth decade, show some familial tendency but have no sex predilection.3 Five percent are associated with neurofibromatosis.4 They usually occur in the adrenal glands, the largest collection of chromaffin tissue in the body, and show a preference for the right side. They are intra-abdominal in 95% of cases, but are palpable in only 15%. In 50% of cases abdominal palpation is said to produce a hypertensive response.2-6
Anatomy and Embryology
Following the adrenals, the most common site