대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Intrathymic parathyroid adenoma

Radiologic Findings

Contrast-enhanced chest CT demonstrates a well-enhancing mass with internal low-attenuated cystic change in the right anterior mediastinum. Elevated Serum PTH level (2811.2 pg/ml) and hypercalcemia suggested hyperparathyroidism. Tc-99 Sestamibi (MIBI) scan showed persistent abnormal uptake in the right anterior mediastinal mass. Mediastinal mass excision was performed, and the pathology confirmed an intra-thymic parathyroid adenoma.
An osteolytic lesion involving right scapula proved to be a giant cell lesion compatible with brown tumor, which is one of the manifestations of hyperparathyroidism.

Brief Review

Most common sites of ectopic location of parathyroid adenoma include thymus, tracheo-esophageal groove, carotid sheath, intrathyroid and para-esophageal locations. The hyper-functioning adenoma is ectopically placed in the mediastinum in 1–2% of cases. This ectopic presentation can be explained by the common embryological origin of thymus and the inferior parathyroid gland, arising from the third pharyngeal pouch and descending together.
Parathyroid adenomas tend to be hypervascular structures with variable contrast enhancement and early washout. Most mediastinal extrathymic parathyroid adenomas can be recognized on CT as small rounded masses, 1-2 cm in diameter, in the upper portion of the anterior mediastinum. Parathyroid scintigraphy shows increased uptake with agents such as Technetium (Tc) 99m Sestamibi (MIBI) (commonly used agent) and Tc-99m tetrofosmin.

References

1. Paige B. Clark, Nancy D. Perrier, Kathryn A. Morton. Detection of an Intrathymic Parathyroid Adenoma Using Single-Photon Emission CT 99mTc Sestamibi Scintigraphy and CT. AJR 2005;184:S16–S18.
2. Nadeem Ul Nazeer Kawoosa, Abdul Majeed Dar, Babar Rashid Zargar Intrathymic parathyroid adenoma. Indian J Thorac Cardiovasc Surg (January–March 2012) 28(1):19–21.
3. Brown, L. R., & Aughenbaugh, G. L. Masses of the anterior mediastinum: CT and MR imaging. AJR 1991;157(6), 1171-1180.
4. Joel R. Smith, M. Elizabeth Oates. Radionuclide Imaging of the Parathyroid Glands: Patterns, Pearls, and Pitfalls. RadioGraphics 2004;24:1101–1115.

Keywords

Mediastinum, Benign tumor,