Parathyroid carcinoma in a dialysis patient definitively diagnosed after parathyroidectomy for uncontrolled secondary hyperparathyroidism

Secondary hyperparathyroidism (SHPT) is a well-known complication in chronic kidney disease patients undergoing maintenance dialysis. In 2006, the Japanese Society for Dialysis Therapy recommended parathyroidectomy (PTx) for medically resistant SHPT cases, resulting in an increase in the performance of PTx. However, after calcimimetics were added to the treatment options in 2008, the number of cases requiring PTx has decreased. Presented here is the case of a dialysis patient with SHPT under medical treatment with calcimimetics, who was normocalcemic but showed persistently high levels of parathyroid hormone (PTH), suggesting the possibility of parathyroid carcinoma. Parathyroid carcinoma is a very rare endocrine malignancy characterized by hypercalcemia and increased PTH level. With appropriately performed PTx at the proper time, the definitive diagnosis was made and the patient has not developed any recurrences or metastases to date. In cases of SHPT refractory to medical therapy, the possibility of parathyroid carcinoma should be considered as an alternative. We report a case in which parathyroid carcinoma was diagnosed after appropriate conversion from medical therapy to PTx with reference to ultrasonographic images.