A 30 year old patient presents to a clinician because of intermittent, severe headaches accompanied by perspiration, palpitations, and pallor. Blood pressure on the initial examination was within normal limits, but, when the patient came in later with a headache, it was 180/135 mm Hg. Urinary vanillylmandelic acid (VMA) levels were elevated. Roughly, what percentage of the tumors causing this pattern is malignant?

The tumor is a pheochromocytoma that intermittently secretes epinephrine and other vasoactive amines, producing episodes of elevated blood pressure accompanied by headache. This is the tumor to associate with the rule of the 10's: 10% malignant, 10% bilateral, 10% extra-adrenal, 10% calcify, 10% occur in kids, and 10% are familial. It is also a orite target on examinations, although the incidence is quite low. Ref: Wyatt C., Butterwoh IV J.F., Moos P.J., Mackey D.C., Brown T.G. (2008). Chapter 18. Endocrine Pathology. In C. Wyatt, J.F. Butterwoh IV, P.J. Moos, D.C. Mackey, T.G. Brown (Eds), Pathology: The Big Picture.