Case Author(s): Rusty Roberts, M.D. and Henry Royal, M.D. , 11/28/04 . Rating: #D3, #Q3
Diagnosis: Metastatic pheochromocytoma
Brief history:
50 y/o woman with new hypertensive episode and long standing hypertension.
Images:
Anterior and posterior whole body I-123 MIBG images.
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Anterior and posterior whole body Tc99m MDP images.
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Axial CT through upper left renal pole with oral contrast only.
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Axial CT through upper pelvis
Full history/Diagnosis is available below
Diagnosis: Metastatic pheochromocytoma
Full history:
50-year-old woman who has 10 year history of hypertension and was diagnosed with a left-sided adrenal mass measuring approximately 5 cm in maximum dimension. She underwent a laparoscopic left adrenalectomy. The patient's pathology was consistent with a pheochromocytoma at that time. There was no description of direct invasion of surrounding soft tissues or vascular invasion. Most recently, the patient has had an exacerbation of her hypertension with a recent blood pressure in the hospital of 248/120. She has also developed recurrent symptoms, including excessive sweating, cold fingertips, palpitations, and recurrent headaches.
Radiopharmaceutical:
MIBG Scintigraphy; 10.15 mci I-123 metaiodobenzylguanidine (MIBG) i.v. and 2 drops SSKI solution p.o. three times daily for 4 days.
Bone Scintigraphy: 21.19 mCi Tc-99m MDP i.v.
Findings:
MIBG: Numerous foci of intense increased uptake consistent with metastatic pheochromocytoma are noted. The foci predominately involve the skull, thoracic spine, lumbar spine, pelvis, bilateral femora. There is also a focus anteriorly within the right hemithorax, either within the chest wall or within the right lung. Note, numerous foci overlie the midline, likely within the spine, however, retroperitoneal lymphadenopathy could have a similar appearance.
MDP: Lesions are seen in the right parietal frontoparietal, left posteroparietal and right temporal bones. Increased uptake at T4, T7 which extends into the medial aspect of the seventh rib, and at T8 and T9. Focal lesion in the lateral aspect of the fourth left rib. Intense uptake at L1 which correlates with a compression fracture at this level on CT performed earlier. Increased uptake in the superior portion of the right ilium which correlates with a lytic lesion in the same area on CT. Increased uptake in the left supra-acetabular region that correlates with the lytic lesion seen on CT. Increased uptake in the right supra-acetabulum that correlates with the lytic lesion seen on CT. Increased uptake in the right intertrochanteric region and midshaft of the right femur.
CT: 1.1 x 1.3 cm nodule in the left adrenal bed concerning for recurrent pheochromocytoma. Lytic iliac lesions are noted on the bone window in the pelvis.
Discussion:
She underwent a CT scan of the abdomen which has a report indicating an approximately 1.1 x 1.3 cm nodule in the left adrenal bed near the lateral aspect of the celiac trunk. The bone scintigraphy was performed prior to the MIBG scintigraphy. It indicated multiple metastases. The MIBG scan showed a focus posteriorly in the upper abdomen, likely representing recurrences in the left adrenal bed and corresponding to his finding on CT scan. Many more metastases were seen on the MIBG scintigram when compared to the MDP scitigram.
Followup:
The patient's 24 hour urine test indicated recurrent elevation of the total metanephrines. This patient's radiographic findings, symptoms, and biochemical findings are consistent with recurrent or metastatic pheochromocytoma.
Major teaching point(s):
I-123 metaiodobenzylguanidine, MIBG, is used for pheochromocytoma and neuorblastoma imaging. It is a precursor of norepinephrine and is taken up selectively by the adrenal medulla, the sympathetic autonomic nervous system, and tumors derived from these tissues.
MIBG can be labeled with either I-131 or I-123. Although it is more expensive, I-123 MIBG is the preferred radiopharmaceutical because of much better image quality. Care must also be taken concerning the patients drug regimen because multiple drugs interfere with the uptake of MIBG.
Also it is important to know the biodistribution of the radiopharmaceutical in question. Comparing the I-123 MIBG and Tc99m MDP images helps to contrast the two agents.
Differential Diagnosis List
Metastatic pheochromocytoma, neuroblastoma, or other neuroectodermal tumor
ACR Codes and Keywords:
References and General Discussion of MIBG Scintigraphy (Anatomic field:Skeletal System, Category:Neoplasm, Neoplastic-like condition)
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Case number: mb001
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