Parathyromatosis in a patient with parathyroid carcinoma and hypercalcemic crisis: Findings on MIBI scan and 4D CT

Abstract

Parathyroid carcinoma is a rare tumor associated with significantly high levels of parathyroid hormone (PTH) and primary hyperparathyroidism (HPT) and is difficult to distinguish from parathyroid adenoma, which is a much more common cause of HPT. Parathyromatosis is a rare condition in which several nodules of hyperfunctioning parathyroid tissue form in the neck and mediastinum, and it presents as recurrent hyperparathyroidism. We describe the case of a 44-year-old woman with recurrent hyperparathyroidism who presented with hypercalcemic crisis and biochemical investigations showed a severely raised serum intact parathyroid hormone (iPTH) level of 2513 pg/ml and serum calcium level of 17 mg/dl. A four-dimensional computed tomography (4D CT) of the neck was done, which showed few arterially enhancing nodular lesions in the right paratracheal and retrotracheal location at the level of thoracic inlet showing washout in delayed images suggestive of recurrent/residual parathyroid lesions. A technetium-99 m methoxyisobutylisonitrile (Tc-99 m MIBI) scan was done, and the planar neck anterior early images showed an area of increased radiotracer uptake in the right lower neck region with persistent uptake in the delayed images. Single photon emission computed tomography/ computed tomography (SPECT/CT) images showed a soft-tissue lesion in the right paratracheal region at the level of C7 vertebra showing increased radiotracer uptake suggestive of a recurrent/residual parathyroid lesion. Exploration and excision of the recurrent parathyroid mass was planned, and the right paratracheal mass with nodes above the aortic arch along with the subcutaneous and intramuscular lesions were excised. Postoperative serum calcium was 7.8 mg/dl, and serum iPTH was 135 pg/ml. Histopathological examination of the excised tissue showed the features of parathyroid carcinoma. Thus, Tc-99 m MIBI scan and 4D CT were critical in evaluating this case of parathyroid carcinoma with recurrent hyperparathyroidism and planning its management.