The parathyroid carcinoma accounts for about 0.5%~5% of the parathyroid neoplasm. Very rarely, but if the intrathyroidal parathyroid gland is present, the carcinoma can be arise in that developmental anomaly. It is very difficult to distinguish thyroid nodule from intrathyroidal parathyroid neoplasm with preoperative radiologic and cytologic evaluations. A 59-year-old man was initially evaluated as follicular thyroid neoplasm accompanied by hyperparathyroidism. He was received the hemi-thyroidectomy with central neck dissection and subtotal parathyroidectomy. The final pathology revealed as intrathyroidal parathyroid carcinoma and hyperplasia of contralateral parathyroid glands. We report very rare and unique clinical situation with a literature review. Key Words; Hyperplasia · Parathyroid glands · Parathyroid neoplasms.