SAT-102 ECTOPIC MEDIASTINAL PARATHYROID CARCINOMA ACCOMPANYING BY PARATHYROID HYPERPLASIA IN A HEMODIALYTIC PATIENT

Abstract

Parathyroid carcinoma is a rare cancer, and the development under secondary hyperparathyroidism is also clinically infrequent. The diagnosis of parathyroid carcinoma under secondary hyperparathyroidism may be difficult due to a radiological similarity between parathyroid carcinoma and adenoma. Moreover, if hemodiaytic patients only show parathyroid hyperplasia without parathyroid adenomatous change by uncontrolled hyperphosphatemia, maligant change of parathyroid gland may be rarely developed. We report an interesting case showing an ectopic mediastinal parathyroid carcinoma related with uncontrolled secondary hyperparathyroidism and parathyroid hyperplasia in patient with end-stage renal disease (ESRD) undergoing hemodialysis. N/A (This abstract is a case report) A 30-year-old man on maintenance hemodialysis due to chronic rejection of transplanted kidney showed a recurrently high level of serum intact parathyroid hormone (iPTH) without remarkable decreases despites of intensive medications including intravenous calcitriol and lanthanum carbonate. Parathyroid scan revealed parathyroid hyperplasia in the both upper portions of thyroid. Ultrasound did not show extrathyroidal nodular lesions. Firstly, simultaneous use of cinacalcet and calcitriol was implemented, and we performed a follow-up scan due to persistently uncontrolled hyperparathyroidism and hypercalcemia. When compared with prior parathyroid scan, it showed more increased parathyroid hyperplasia in the same area, and new hot lesions in left lower portion of thyroid and right upper paratracheal area in mediastinum were newly shown. Computed tomography (CT) of neck showed multiple nodular lesions in the mediastinal area, compatible with ectopic parathyroid adenoma, along with hyperplasia on both upper and left lower parathyroid glands. Firstly, we referred to thoracic surgery for the mediastinal mass. The preoperative laboratory results were as follows: serum calcium, 10.4 mg/dL; serum iPTH, 1150 pg/mL. The mediastinal masses with diameters of less than 2.2 cm were removed and histologically compatible with parathyroid carcinoma. Serum iPTH did not postoperatively decrease, but serum calcium decreased. We performed a 18F-fluorodeoxyglucose positron-emission tomography-CT scan for parathyroid gland and distant metastases of parathyroid carcinoma. It revealed no locoregional and distant metastases of parathyroid carcinoma except remained parathyroid hyperplasia. We recommended total thyroidectomy immediately due to uncontrolled secondary hyperparathyroidism. After one month, the patient was performed total thyroidectomy and serum iPTH level was normalized after the operation. The pathologic results after total thyroidectomy showed only parathyroid hyperplasia without adenomatous changes and it also revealed no locoregional metastatic lesion of parathyroid carcinoma. A diagnosis of parathyroid carcinoma without a confirmative surgery is difficult particularly in uncontrolled secondary hyperparathyroidism without parathyroid adenoma. Moreover, an ectopic mediastinal parathyroid carcinoma under same condition may be easily underdiagnosed. Thus, dialytic patients with refractory secondary hyperparathyroidism irregardless of existence of parathyroid adenoma should perform a radiologically close follow-up, even if the first scan show only parathyroid hyperplasia.