**Core Concept**
Pheochromocytomas are rare, catecholamine-secreting tumors arising from the adrenal medulla. They are characterized by excessive production of epinephrine (adrenaline) and norepinephrine, leading to hypertension, tachycardia, and other systemic symptoms.

**Why the Correct Answer is Right**
Pheochromocytomas are typically benign, but they can be malignant in some cases. They are often associated with genetic syndromes such as multiple endocrine neoplasia (MEN) type 2 and von Hippel-Lindau disease. The hallmark of pheochromocytomas is the excessive production of catecholamines, which can lead to hypertension, tachycardia, and other systemic symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because pheochromocytomas are typically benign, but they can be malignant in some cases.
**Option B:** This option is incorrect because pheochromocytomas are often associated with genetic syndromes such as multiple endocrine neoplasia (MEN) type 2 and von Hippel-Lindau disease.
**Option C:** This option is incorrect because the excessive production of catecholamines is a hallmark of pheochromocytomas, leading to hypertension, tachycardia, and other systemic symptoms.

**Clinical Pearl / High-Yield Fact**
It is essential to consider pheochromocytoma in the differential diagnosis of hypertension, especially in patients with a family history of the disease or those with symptoms such as tachycardia and sweating.

**Correct Answer: D.**