A 42-year-old Indian man presents with episodic severe headaches, profuse sweating, and palpitations for 3 months. Blood pressure is 165/105 mmHg during an episode and 145/90 mmHg at baseline. Imaging reveals a well-circumscribed, encapsulated adrenal medullary tumor (marked **A** in the diagram). Biochemical testing confirms elevated plasma-free metanephrines. Which of the following best describes the cellular origin and functional consequence of the structure marked **A**?
A. Adrenocortical tumor cells; causes hypokalemia and metabolic alkalosis
B. Paraganglionic neural crest cells of the organ of Zuckerkandl; presents with orthostatic hypotension
C. Steroid-secreting fasciculata cells; sustained hypertension due to aldosterone excess
Catecholamine-secreting chromaffin cells of the adrenal medulla; episodic release causes paroxysmal hypertension, headache, and diaphoresis
D.
Explanation
Why option 1 is correct
The structure marked A is a pheochromocytoma — a catecholamine-secreting tumor arising from chromaffin cells of the adrenal medulla. These cells normally secrete norepinephrine and epinephrine in response to sympathetic stimulation. When neoplastic, they release catecholamines episodically and uncontrollably, producing the classic triad of paroxysmal hypertension, headache, and diaphoresis (sweating), often accompanied by palpitations, tremor, and anxiety. This is the defining pathophysiology of pheochromocytoma and is directly stated in Robbins Basic Pathology and Endocrine Society 2014 guidelines. The patient's clinical presentation and biochemical confirmation (elevated plasma-free metanephrines) are pathognomonic.
Why each distractor is wrong
Option 2: Steroid-secreting fasciculata cells produce cortisol and cause sustained (not episodic) hypertension with hypokalemia and metabolic alkalosis — this describes adrenocortical carcinoma or Cushing syndrome, not pheochromocytoma. The tumor in A is medullary, not cortical.
Option 3: Paragangliomas arise from extra-adrenal paraganglia (e.g., organ of Zuckerkandl), not from the adrenal medulla itself. While paragangliomas are catecholamine-secreting and can present similarly, the diagram explicitly labels A as an adrenal medullary tumor. Paragangliomas do not typically present with orthostatic hypotension.
Option 4: Adrenocortical tumors produce steroid excess (cortisol, aldosterone, or androgens) and cause hypokalemia and metabolic alkalosis — not the episodic catecholamine-driven symptoms seen here. The histology and biochemistry exclude cortical pathology.
High-YieldNEET PG
Pheochromocytoma = chromaffin cell tumor of adrenal medulla → episodic catecholamine release → classic triad (paroxysmal HTN, headache, diaphoresis); diagnosis is biochemical (plasma-free metanephrines) FIRST, then imaging.
Robbins Basic Pathology 11e; Endocrine Society 2014
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