According to the rule of 10s, what percentage of pheochromocytomas occur in children?

• A. 5%
• B. 15%
• C. 10%
• D. 20%

Answer: (C)

The rule of tens states that about 10% of pheochromocytomas occur in children. Historically, this rule highlighted several ten-percent truths about pheochromocytomas, including that a similar fraction are bilateral, malignant, or familial, and that about 10% arise outside the adrenal gland. When applying this general rule to age distribution, roughly one in ten cases would be seen in children, which corresponds to 10%. The other percentages (5%, 15%, 20%) don’t fit this traditional guideline, which is why 10% is the best answer. Keep in mind that newer data can shift exact figures with advances in genetics, but the classic rule still points to about 10%.