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PARATHYROID CARCINOMA
Authored By: Peter Phan and Jerold Wallis, Assoc Prof of Radiology.
Patient: 64 year old male
History:

The patient is a 64 year old male with persistent hyperparathyroidism.   He underwent a parathyroid scintigraphy at an outside hospital.  A second parathyroid scintigraphy was performed at our institution.

Image Size:[small][as-submitted]

Fig. 1
Initial parathyroid scintigraphy at an outside hospital. First image has marker on sternal notch.

Fig. 2
Second parathyroid scintigraphy study performed at our institution

Fig. 3
SPECT images of the second parathyroid scintigraphy

Fig. 4
Thyroid ultrasound
Image Size:[small][as-submitted]

Findings: Initial Study: 

RADIOPHARMACEUTICAL: 20 mCi Tc-99m sestamibi i.v.

Intense focal uptake in the region of the right lower thyroid lobe, which does not persists on delayed imaging at 3.5 hours.



Second Study:  

RADIOPHARMACEUTICAL: 22 mCi Tc-99m sestamibi i.v.

The right lower thyroid lobe uptake is again seen, but with delayed imaging at 2 hours, the lesion clearly persists.  The SPECT images suggest that this lesion may be located posterior (or at least extends posterior) to the right thyroid lobe.

DDx: 1) Parathyroid adenoma

2) Parathyroid carcinoma

3) Thyroid adenoma

4) Thyroid carcinoma
Diagnosis: Parathyroid carcinoma
General Discussion: Given its location posterior to the right thyroid lobe, its persistent retention of radiotracer, and the patient's clinical history of hyperparathyroidism, this lesion is most likely a parathyroid adenoma or carcinoma.  Its large size and heterogenous appearance on ultrasound makes a parathyroid carcinoma a strong possibility.

The initial study described this lesion as likely to be thyroid in origin because of the lack of persistent uptake.  However, because the delayed images were performed at 3.5 hours (standard delayed imaging is at 2 hours), activity within the parathyroid lesion had washout, resulting in a "false negative".

Tc-99m sestamibi localizes to cellular cytoplasm and mitochondria.  It is believe that the substantial number of mitochondria oxyphil cells of parathyroid adenomas results in the significant uptake and delayed washout of the radiotracer relative to the surrounding tissue [1].  However, note that not all parathyroid adenomas retain sestamibi on delayed imaging.
References: Harvey Ziessman, Janis O'Malley, James Thrall. Nuclear Medicine: the Requisite in Radiology. 3rd editon. Mosby, 2006, pg 103.
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Additional Details:

Case Number: 108817Owner(s): Peter Phan and Jerold Wallis, Assoc Prof of RadiologyLast Updated: 02-07-2013
Anatomy: Face and Neck   Pathology: Neoplasm
Modality: Nuc MedAccess Level: Readable by all users, writable by NucMed Certifiers
Keywords: panmACR: 27400.00000, 20000.37300

Case has been viewed 46 times.
Certified by Jerold Wallis on 05-14-2008

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