Question:medium
Which of the following imaging modalities is most sensitive for evaluation of extra-adrenal pheochromocytoma?
Which of the following imaging modalities is most sensitive for evaluation of extra-adrenal pheochromocytoma?
Show Hint
Extra-adrenal or multiple pheochromocytomas need a whole-body, tissue-specific scan, not just a regional anatomical one.
Updated On: Jul 8, 2026
- USG
- CT
- MRI
- MIBG scan
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Question:
We need the imaging test that best finds pheochromocytoma tissue lying outside the adrenal gland, which can be anywhere in the sympathetic chain.
Step 2: Key Formula or Approach:
Anatomical scans, USG, CT, and MRI, only show structure in the region they cover. A functional scan instead follows a tracer that is taken up specifically by the tumor cells, wherever they sit in the body.
Step 3: Detailed Explanation:
MIBG behaves like norepinephrine and is actively absorbed by chromaffin cells through their noradrenaline transporter. A radiolabeled MIBG scan therefore surveys the whole body in one go and lights up any chromaffin tissue, including small, multiple, or ectopic extra-adrenal tumors that a CT of just the abdomen could easily miss. USG has poor sensitivity outside the adrenal bed and for small lesions. CT and MRI show anatomy well but cannot tell functioning tumor tissue from a look-alike mass, and both are usually done as regional studies rather than whole-body surveys.
Step 4: Final Answer:
MIBG scan is the most sensitive of the four options for extra-adrenal pheochromocytoma because it is a whole-body, tumor-specific functional test.
We need the imaging test that best finds pheochromocytoma tissue lying outside the adrenal gland, which can be anywhere in the sympathetic chain.
Step 2: Key Formula or Approach:
Anatomical scans, USG, CT, and MRI, only show structure in the region they cover. A functional scan instead follows a tracer that is taken up specifically by the tumor cells, wherever they sit in the body.
Step 3: Detailed Explanation:
MIBG behaves like norepinephrine and is actively absorbed by chromaffin cells through their noradrenaline transporter. A radiolabeled MIBG scan therefore surveys the whole body in one go and lights up any chromaffin tissue, including small, multiple, or ectopic extra-adrenal tumors that a CT of just the abdomen could easily miss. USG has poor sensitivity outside the adrenal bed and for small lesions. CT and MRI show anatomy well but cannot tell functioning tumor tissue from a look-alike mass, and both are usually done as regional studies rather than whole-body surveys.
Step 4: Final Answer:
MIBG scan is the most sensitive of the four options for extra-adrenal pheochromocytoma because it is a whole-body, tumor-specific functional test.
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