Pheochromocytoma — Death of an Axiom

Abstract

Medical students often learn axioms in order to remember the key features of a disorder. The “rule of 10” used to describe pheochromocytomas is a good example: 10 percent are extraadrenal, and of those, 10 percent are extraabdominal; 10 percent are malignant; 10 percent are found in patients who do not have hypertension; and finally, 10 percent are hereditary.¹ Familial pheochromocytoma is inherited as an autosomal dominant trait alone or as a component of the multiple endocrine neoplasia type 2 syndromes (MEN-2A and MEN-2B), von Hippel–Lindau disease, or, in rare cases, neurofibromatosis type 1.² The remaining 90 percent of pheochromocytomas . . .