Endocrinol Metab.  2012 Mar;27(1):83-88. 10.3803/EnM.2012.27.1.83.

Primary Hyperaparathyroidism due to Cystic Parathyroid Adenoma not Detected on 99mTc-Sestamibi Scan

• Khang AR
• Kim EK
• Nam EY
• Byeon SJ
• Kim JH
• Ohn JH
• Hong ES
• Choi HJ
• Jung KC
• Sung MW
• Shin CS
• Park KS
• Kim SY

• KMID: 2134824
• DOI: http://doi.org/10.3803/EnM.2012.27.1.83

Abstract

Parathyroid cysts, which can be divided into functional and non-functional cysts, are rare causes of primary hyperparathyroidism. A technetium-99m-methoxyisobutylisonitrile (99mTc-sestamibi) parathyroid scan is a sensitive diagnostic tool for the localization, although it sometimes shows a false-negative result. Here we report a case of presumed cystic parathyroid adenoma based on clinical findings and analysis of cystic fluid with negative findings in a parathyroid scan. A 44-year-old male patient visited the hospital due to leg pain and compressive symptoms (dysphagia, hoarseness) that had started 4-5 months before. His serum calcium level was 14.4 mg/dL and his intact parathyroid hormone (iPTH) had increased to 478.1 pg/mL. On neck computed tomography, a cystic nodule measuring 6.2 cm was detected in the inferior part of the right thyroid gland. Sestamibi uptake for this nodule was not detected on 2-h delayed imaging, and fluorodeoxyglucose positron emission tomography showed only subtle uptake. Fine-needle aspiration was performed and intracystic iPTH had increased to 61,600 pg/mL. Focused parathyroidectomy guided by intraoperative iPTH monitoring led to successful enucleation of the right inferior parathyroid gland. A parathyroid adenoma was confirmed, and his laboratory results had normalized. This study shows that cystic parathyroid adenoma can sometimes be difficult to detect on a 99mTc-sestamibi parathyroid scan.

Keyword

Hyperparathyroidism; Parathyroid neoplasms; Technetium Tc 99m sestamibi

MeSH Terms

Adult
Biopsy, Fine-Needle
Calcium
Humans
Hyperparathyroidism
Hyperparathyroidism, Primary
Leg
Male
Neck
Parathyroid Glands
Parathyroid Hormone
Parathyroid Neoplasms
Parathyroidectomy
Positron-Emission Tomography
Technetium Tc 99m Sestamibi
Thyroid Gland
Calcium
Parathyroid Hormone
Technetium Tc 99m Sestamibi

Figure

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  Fig. 1 Neck computed tomography shows a cystic lesion that measured 6.2 × 3.8 × 2.7 cm on the inferior side of the right thyroid lobe.

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  Fig. 2 After injection of 555 MBq (15 mCi) 99mTc-sestamibi, dual-phase scintigraphy was performed. Early (A, at 15 minute) and late (B, at 2.5 hour) images of the anterior neck were obtained using a low-energy high-resolution parallel-hole collimator. There was no 99mTc-sestamibi accumulation corresponding to the cystic lesion detected by neck computed tomography on either the early (A) or delayed (B) images.

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  Fig. 3 Fluorodeoxyglucose positron emission tomography showed subtle uptake on the lower lobe of right thyroid gland.

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  Fig. 4 Gross and microscopic findings of enucleated parathyroid adenoma. A. The tumor was encapsulated and cut surface showed brown color and cystic change. B. Low power view of parathyroid gland showing solid and cystic area (H&E stain, × 0.5). C. The solid area of tumor was showed hypercellular chief cells and well-vascularized (H&E stain, × 200). D. The cystic area of tumor showed vacant cavity with hemorrhage (H&E stain, × 200).

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