**Core Concept**
Pheochromocytoma is a rare, catecholamine-secreting tumor of the adrenal gland, characterized by excessive production of epinephrine and norepinephrine. The "rule of 10" in pheochromocytoma refers to various clinical and biochemical features that are commonly observed in patients with this condition.

**Why the Correct Answer is Right**
The rule of 10 includes the following characteristics: 10% of pheochromocytomas are extra-adrenal, 10% are malignant, 10% are bilateral, 10% occur in children, 10% are familial, and 10% occur in patients with a family history of pheochromocytoma. These features highlight the complexity and variability of this condition.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not a part of the rule of 10 in pheochromocytoma. The rule of 10 does not include the percentage of patients with hypertension or hypokalemia as a characteristic.
* **Option B:** This option is not a part of the rule of 10 in pheochromocytoma. The rule of 10 does not include the percentage of patients with a family history of hypertension as a characteristic.
* **Option C:** This option is not a part of the rule of 10 in pheochromocytoma. The rule of 10 does not include the percentage of patients with a history of trauma as a characteristic.
* **Option D:** This option is not a part of the rule of 10 in pheochromocytoma. The rule of 10 does not include the percentage of patients with a history of malignancy as a characteristic.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that pheochromocytomas are often "silent" tumors, meaning they may not cause any symptoms until they are large enough to cause catecholamine excess. This highlights the importance of a high index of suspicion and timely diagnosis in patients with suspected pheochromocytoma.

**Correct Answer:** B.