Primary hyperparathyroidism is usually caused by parathyroid adenoma; however, parathyroid carcinoma is a rare cause. We report a rare case of 74-year-old female of primary hyperparathyroidism caused by parathyroid carcinoma (PC) and coexisting multiple parathyroid adenomas. She was referred to our hospital for primary hyperparathyroidism and a suspected thyroid tumor. She had no family history of malignant tumor. Computed tomography (CT) and ultrasonography of the neck revealed some masses posterior to both thyroid lobes. Those masses were believed to be parathyroid lesions. However, another mass located posterior to the right upper thyroid lobe seemed to be heterogeneous, which indicated a malignant thyroid tumor as well as parathyroid tumor. The preoperative diagnosis was multiple parathyroid adenoma and suspicious incidental thyroid carcinoma. Therefore, the patient underwent total parathyroidectomy and thyroidectomy. The histopathological diagnosis was parathyroid carcinoma coexisting with multiple parathyroid adenomas. There was no evidence of recurrence at 1 year after the surgery. It was difficult to diagnose PC preoperatively. Few rare cases of PC coexisting with parathyroid adenoma in multiple endocrine neoplasia type 1 (MEN1) have been reported. Therefore, careful follow-up was necessary considering the possibility of MEN1, though she did not wish for a genetic examination.
Keywords: Multiple parathyroid adenoma; Parathyroid adenoma; Parathyroid carcinoma; Primary hyperparathyroidism.