Sonography Findings in Parathyroid Carcinoma and Heterogenous Parathyroids

Abstract

Parathyroid carcinoma is a rare endocrine neoplasm accounting for less than 1% cases of primary hyperparathyroidism, with incidence rates varying between 0.5% and 5% between various case series (Givi and Shah 2010). Parathyroid carcinoma is usually seen in the elderly with peak incidence being in the fourth decade of life (Givi and Shah 2010). There is no gender predilection for parathyroid carcinoma unlike parathyroid adenoma, which is three to four times more common in females than males. Parathyroid carcinoma is sporadic and may also be a part of familial syndromes, particularly in HPTT-JT (hyperparathyroidism-jaw tumour) syndrome. Majority of parathyroid carcinoma are functional, and clinical symptoms at presentation are due to severe hypercalcaemia due to hypersecretion of parathyroid hormone. The elevated serum calcium levels are often in the range of 13–15 mg/dL, and the elevated serum parathyroid levels are often beyond 3000 to 5000 pg/L. As the clinical presentation is that of severe hyperparathyroidism, a finding that is also seen in benign parathyroid enlargements, parathyroid carcinoma is often diagnosed at the time of surgery and subsequent histopathology. Technetium-99m sestamibi findings are similar to that of an adenoma and do not differentiate between the two. Ultrasound imaging can identify heterogeneity of the parathyroid enlargement and may reveal indistinct margins from the adjacent thyroid. The capsular margins of both the parathyroid nodule and the adjacent thyroid are not clearly identified, often rendering demarcation of the cleavage plane between the thyroid and the parathyroid difficult. On colour Doppler, the vascular pattern may appear to be chaotic and heterogeneous, instead of the characteristic arc rim vascularity.