Endocrine Abstracts

Background: Parathyroid carcinoma (PC) is an infrequent pathology, responsible for 0.5–5% of primary hyperparathyroidism cases. Despite the high prevalence of secondary hyperparathyroidism in patients with a chronic kidney disease (CKD), PC among them is extremely rare, with less than 30 cases reported in the literature. The diagnosis of PC in CKD patients is more complex, because of using cinacalcet that reduces the level of calcium and parathyroid hormone (PTH). We report a case of intrathyroidal PC in patients with CKD that was successfully treated by en-bloc resection of the tumor.

Clinical case: A 57-year-old man who had received regular hemodialysis, applied to our center because of uncontrolled hypercalcemia and hyperphosphathemia. He had been treated with cinacalcet 120 mg and sevelamer 4800 mg per day and his laboratory findings were as follows: calcium (Ca) – 2.92 mmol/l (range 2.1–2.55 mmol/l), phosphate (P) – 1.96 mmol/l (0.74- 1.52 mmol/l), PTH – 1983 pg/ml (15-65), alkaline phosphatase – 597 u/l (50-150). Ultrasonography showed an enlarged parathyroid gland (PG) on the right upper side of the thyroid gland with uneven contours of 3.0 x 3.0 x 2.3 cm with calcinate, that was confirmed by CT-scan and 99mTc-Sestamibi scintigraphy. No other PG were identified. During a surgery, intrathyroidal parathyroid tumor was detected that had no clear boundary with the right lobe of the thyroid gland. A locally invasive tumor of the right upper PG and enlargement of the other three parathyroid glands were found during bilateral neck exploration. An en-bloc resection of the upper right PG was performed with the right thyroid lobe, surrounding tissue and paratracheal lymph nodes with subtotal parathyroidectomy of the three enlarged PG. PTH and Ca decreased down after surgery that required taking 2,5 mcg of alfacalcidol and 1,5 g of calcium carbonate per day. Intrathyroidal PC was confirmed by a histological examination that identified vascular and capsular invasion and foci of necrosis. The immunohistochemical study with PTH revealed a positive reaction and confirmed the histogenesis of the tumor from the parathyroid tissue, Ki67 was 5–7%. Three months after surgery the laboratory examination showed: Ca – 2,08 mmol/l, PTH – 117 pg/ml, P – 0.53 mmol/l.

Conclusion: Our case indicates that the use of cinacalcet can hinder the diagnosis of PC in a chronic dialysis patient. When uncontrolled hypercalcemia and/or hyperphosphathemia develop during cinacalcet administration, PC should be suspected, and the appropriate surgery should be planned.