What is the primary characteristic of pheochromocytoma?

Pheochromocytoma is primarily characterized as a small vascular tumor located in the adrenal medulla. This tumor arises from chromaffin cells, which are responsible for producing catecholamines (such as epinephrine and norepinephrine). The overproduction of these hormones leads to characteristic symptoms including episodic headaches, palpitations, sweating, and hypertension.

This description aligns directly with the nature of pheochromocytomas as they are typically benign, and while they can sometimes present as malignant, the tumor itself originates specifically from the adrenal medulla rather than the adrenal cortex. The emphasis on vascularity highlights the tumor's ability to cause significant physiological effects due to its hormone secretion.

Other options suggest misconceptions about the nature of pheochromocytoma, such as implying benign hormone secretion without acknowledging the tumor's hormonal activity and its specific location in the adrenal medulla. Additionally, significant weight gain is not a typical characteristic of pheochromocytoma; rather, patients may experience weight loss due to the effects of excess catecholamines. Lastly, the assertion that pheochromocytoma is exclusively a malignant tumor of the adrenal cortex is false, as these tumors can be benign and originate from the medulla, not the cortex.