Presentation
Patient had nephrocalcinosis, hypercalcemia and hyperparathyroidism. PTH (1-84) = 11.0 pmol/L (normal range 1.6 - 6.0).
Patient Data
A small candidate parathyroid lesion which is external to thyroid (located inferior to isthmus, superior to brachiocephalic trunk), size 0.9 x 0.9 x 0.9 cm (AP x W x CC), associated with adjacent prominent feeding artery and draining vein, giving rise to "polar vessel" sign. This aforementioned lesion has mean attenuations of 30HU (plain), 100HU (arterial phase), 75HU (portovenous phase) which are consistently less than the attenuation of thyroid gland - type C enhancement pattern.
Asymmetry of thyroid gland in which right hemithyroid is slightly larger than the left. No retrosternal extension.
A small heterogeneous hypoechoic lesion which is external to thyroid (located inferior to isthmus, superior to brachiocephalic trunk), size 0.9 x 0.9 x 0.9cm (AP x W x CC), associated with adjacent prominent feeding artery and draining vein, giving rise to "polar vessel" sign. Findings are suggestive of candidate parathyroid lesion.
Predominantly isoechoic solid thyroid nodule at mid to lower pole of right hemithyroid, size 0.9 x 1.0 x 1.1 cm (AP x W x CC), no punctate echogenic foci/calcification - TIRADS 3 but size < 1.5 cm.
Another small hypoechoic thyroid nodule at isthmus, size 0.3 x 0.6 x 0.8 cm (AP x W x CC) with extra-thyroidal extension, no punctate echogenic foci/calcification - TIRADS 5 but size < 1.0 cm. Suggest USG follow-up.
Bilateral multi-focal calcific densities over renal shadows.
Surgical clip at gallbladder fossa (past surgical history of cholecystectomy for cholelithiasis).
Parathyroid 4D CT and complementary ultrasound demonstrated a candidate lesion (external to thyroid, located inferior to isthmus, superior to brachiocephalic trunk), associated with polar vessel sign is most likely parathyroid in origin (intermediate to high confidence). However, lymph node remains a diagnostic possibility.
Patient underwent parathyroidectomy for the reported candidate parathyroid lesion.
Histopathology Examination Report:
An irregular brownish tissue weighing 0.8 g and measuring 14 x 11 x 9 mm. Bisected and entirely submitted in one block.
Microscopy: Section shows well-circumscribed parathyroid tissue composed of a mixture of chief cells, oxyphil cells, and smaller amounts of water clear cells. The tissue displays nodular expansion of the cellular components with loss of central fatty tissue. The cells are arranged in sheets and compact acini, punctuated by delicate small blood vessels. The chief cells display bland, centrally round nuclei with moderate pale cytoplasm. The oxyphil cells show uniform, bland looking hyperchromatic round nuclei with abundant eosinophilic granular cytoplasm, while the water clear cells show abundant clear cytoplasm with prominent cell borders. No prominent nuclear pleomorphism or mitosis seen. Some of the glands and blood vessels are dilated. No necrosis, lymphovascular invasion, or perineural invasion identified. Smaller amounts of native parathyroid tissue is seen displaced to the periphery, containing clusters of fatty tissue.
Interpretation: Consistent with parathyroid adenoma.
Case Discussion
Ultrasound examination is operator dependent. The small parathyroid lesion was not detected during the initial ultrasound examination. Sestamibi scan showed a suspicious parathyroid adenoma at right thyroid gland. Hence, patient was scheduled for Parathyroid 4D CT for preoperative localization of parathyroid adenoma.
The anticipated size of parathyroid adenoma is usually proportionate to the elevated level of parathyroid hormone (PTH). In spite of slightly elevated parathyroid hormone level, parathyroidectomy was indicated for this patient with symptomatic hyperparathyroidism.
Recent studies have shown that parathyroid 4D CT is superior to detect small parathyroid lesion with increased accuracy than sonography and scintigraphy for preoperative localization of parathyroid adenomas.
Sestamibi scan (SPECT-CT) lacks accuracy in detecting small parathyroid lesions. In this case, the nuclear medicine physician was able to detect the presence of small parathyroid adenoma but reported it as intrathyroidal in location.
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