Giant cystic parathyroid adenoma with thrombosis of internal jugular vein seen on CT and Tc-99m methoxy isobutyl isonitrile parathyroid scan.

Primary hyper-parathyroidism is attributed by a solitary parathyroid adenoma in 80-85% cases and mostly are non-palpable and needs imaging for localization. Cystic degeneration of parathyroid adenoma is rarely seen in primary hyperparathyroidism. We are presenting a case of giant cystic functioning parathyroid adenoma with associated localized co-morbids.

INTRODUCTION

Parathyroid scintigraphy using Tc-99m methoxy isobutyl isonitrile (MIBI) has become a popular imaging modality for localization of functioning parathyroid adenoma. It is considered more important in cases of multi-glandular disease. Localization of adenoma by scintigraphic technique, signs and symptoms has good correlation with size of the adenoma.

CASE REPORT

A 54-year-old female presented with 3 years history of bony pains, muscle weakness, fatigue, and depression with soft tissue swelling over left thyroid bed and left upper limb. Serum calcium and parathormone levels were abnormally high (17.4 mg/dl and 1182 pg/ml, respectively). Tc-99m MIBI scan revealed a large area of non-homogenous tracer uptake over left thyroid bed and superior mediastinum displacing the thyroid toward right [Figure 1]. In view of raised serum calcium and parathormone levels, it was considered a cystic parathyroid adenoma as non-functional (true) parathyroid cysts are also a known entity.[1] An associated cold defect has been reported in patients with cytsic parathyroid adenoma.[2] Cytic adenomas have been reported to occur in hypercalcemic crisis as the result of acute necrosis or hemorrhage of a parathyroidadenoma.[3]

Figure 1

Planar (dual phase) Tc-99m MIBI scan ((a) Anterior chest view at 10 min. (b) 15 min anteriro neck view. (c) 1 h anterior neck view) a large area of non-homogenous tracer uptake over left lower thyroid region with retrosternal extension (arrow) and gross displacement of both lobes of thyroid to right

Computed tomography scan showed a large left-sided parathyroid adenoma with marked cystic changes and thrombosis of left internal jugular vein [Figure 2]. Cystic degeneration of parathyroid adenoma is reported in 1-2% cases with primary hyperparathyroidism,[45] and 4% of abnormal parathyroid glands.[6] Thrombosis of left internal jugular vein has been reported in few case reports.[7] Excisional biopsy revealed cystic parathyroid adenoma with no evidence of malignancy.

Figure 2

Computed tomography scan ((a) Axial. (b) Coronal. (c) Saggital) shows a large hypodense area with enhancing wall (long arrow) over left side of neck extending into retrosternal region and deviating the trachea to right. This represents cystic degeneration of parathyroid adenoma. Thrombosis of left internal jugular vein (short arrow) is also appreciable