Large parathyroid carcinoma eight years after thyroid surgery

Sixty three 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 2013 neck ultrasonography (US) displayed a homogeneous, hypoechoic mass 1.8x1.9cm in size. No routine follow up or US examinations were done. In 2020 Laboratory analysis showed elevated PTH (1241.9 pg/mL) and calcium (3.42 mmol/l). Multiparametric neck ultrasonography was perfomed: B-mode examination revealed a hypoechoic, irregular, nonhomogeneous mass sized 5.5x3.2x5.0 cm with multiple central calcifications and mixed vascularisation pattern on colour doppler and superb microvascularisation imaging modilites. Mass appeared less elastic on Shear wave elastography compared to normal thyroid tissue (28.8kPa and 16.8kPa respectively). Contrast enhanced ultrasound (SonoVue) showed diffuse, homogenous hypervascularity in early arterial phase - 6s, quickly reaching peak contrast concentration - 12s, following homogenous early washout 23s. Computed tomography revealed irregular mass in proximity to trachea, oesophagus, slight dislocation of common carotid artery. Perifocal fatty tissue appeared normal. Scintigraphy displayed a suspect parathyroid tumor or suspect left lobe nodule of thyroid. Cytological analysis were suspicious of a follicular neoplasm (BETHESDA IV). Based on the biochemical diagnosis of primary hyperparathyroidism and radiological examinations a suspect parathyroid tumor was considered. Intraoperative findings demonstrated 9x6cm tumor adjacent to the external carotid artery laterally and recurrent laryngeal nerve medially. PTH levels before surgery 1545.4 pg/ml, during 1287.8 pg/ml, 20 min after resection 120.8 pg/ml, 6h after 17.2 pg/ml, next day - 13.4 pg/ml, next day calcium - 2.77mmol/l. Pathohistological examination revealed tumor solid in structure, with focal necrosis, penetrating the capsule. Immunohistochemical analysis was positive for chromogranin, CD56, Ki-67 (8-10%) and negative for CK20 and CK7. The morphological and immunohistochemical results correspond to parathyroid carcinoma, known as rare entity among parathyroid lesions (1 %).