Endocrine Abstracts

Introduction.: Parathyroid carcinoma (PC) is the one of the rarest endocrine malignances and occurs in 0.5–5% of cases among patients with primary hyperparathyroidism (PHPT). Diagnosis of PC can be challenging and often made after surgery or while local or distant metastases detection. We present a case of a patient with a large intrathyroid PC, which was initially identified as a malignant thyroid nodule.

Case report.: 59-old caucasian women was diagnosed with 3.2 cm cystic-solid nodule in the right thyroid lobe with irregular margins and increased blood flow in Jun? 2020. FNAB was performed and papillary cancer suggested (Bethesda V). At presentation: TSH – 1.01 mME/ml (RR: 0.4–4.0), calcitonin <2.0 pg/ml (RR: 0–5), Ca – 3.19 mmol/l (RR: 2.0–2.57), PTH – not defined. Thyroidectomy and central neck lymph node dissection were performed. Intraoperative cytology suggested a follicular neoplasia. Follicular variant papillary thyroid cancer with no signs of lymph node lesion was confirmed histologically (pT3N0M0). Immunohistochemistry was not performed. In September 2020 patient underwent adjuvant RAI ablation (I-131, 3.7 GBq). In February 2022 hypercalcaemia with Ca 3.15 mmol/l (RR: 2.0–2.65), Ca²⁺ – 1.75 mmol/l (RR: 1.12–1.32) was detected and PHPT suspected. PTH – 1424 pg/ml (RR: 12–88) when measured. Neck US, 99mTc-sestamibi parathyroid SPECT scintigraphy, ?ontrast-enhanced Neck and Chest CT showed no evidence of disease in the neck and chest. The hypervascular liver tumor 33×23 mm with irregular margins was detected during abdominal CT.

In April 2022 the liver resection (segment VIII) was performed. Severe hypercalcemia before surgery was corrected with intravenous bisphosphonates and cinacalcet. Hungry bone syndrome after surgery confirmed a successful outcome.

Positive immunostaining for GATA-3, CKpan, CD56, PAX8 in the liver tumor, positive immunostaining for GATA-3, CKpan, CD56, PAX8 and negative immunostaining for thyroglobulin and TTF-1 in the primary thyroid tumor confirmed the diagnosis of intrathyroid PC with single liver metastasis 2 years after the initial surgery.

Conclusion.: Our case demonstrates, that cytology and routine histology are poor at distinguishing malignant thyroid and parathyroid tumors. To avoid faults in treatment, it is extremely important to exclude PHPT before surgery in hypercalcaemic patients with suspected thyroid cancer.