Large Parathyroid Tumor 8 Years after Thyroid Surgery: A Case Report.

This report represents an unusually large parathyroid carcinoma (PC) mimicking thyroid nodule recurrence after hemithyroidectomy. PC is a rare endocrine malignancy accounting for less than 1% of hyperparathyroidism cases. This is the first case report where contrast-enhanced ultrasound (CEUS) was performed on a PC. A 63-year-old female presented with an enlarged mass on the left side of the neck. In 2012, left-side hemithyroidectomy was done due to a benign goiter. In 2020, laboratory analysis showed markedly elevated parathyroid hormone and calcium. Multiparametric neck ultrasonography was performed including B-mode, color Doppler, shear wave elastography, and CEUS. Computed tomography revealed an irregular mass in proximity to the trachea, esophagus, and dislocation of the common carotid artery. Perifocal fatty tissue appeared normal. Scintigraphy displayed a suspected parathyroid tumor or a suspected left lobe nodule of thyroid. Based on the biochemical diagnosis of primary hyperparathyroidism and radiological examinations, a suspected parathyroid tumor was considered. Intraoperative findings demonstrated an unusually large 9 × 6 cm tumor (84 g) adjacent to the common carotid artery anterolaterally and the recurrent laryngeal nerve medially. Pathohistological examination revealed a tumor solid in structure, with focal necrosis penetrating the capsule. Immunohistochemical analysis was positive for chromogranin, CD56, and Ki-67 (8-10%) and negative for CK20 and CK7. The morphological and immunohistochemical results correspond to PC. PC is a challenging diagnosis requiring a multidisciplinary approach, especially in the case of previous neck surgery. The only curative treatment for PC is radical surgery. Lifelong monitoring of PCs is mandatory due to the high recurrence rate.