Most cases of primary hyperparathyroidism are due to either a parathyroid adenoma or parathyroid hyperplasia. Parathyroid carcinoma is a very rare cause of hyperparathyroidism. Although the diagnosis of parathyroid carcinoma is usually established by pathologic criteria especially of vascular or capsular invasion, some clinical and biochemical features differentiate it from benign forms of hyperparathyroidism. We undertook a retrospective study in 4 patients with functioning parathyroid carcinoma, with the aim of conveying experience from management of this rare cause of kyperparathyroidism.

Clinical simptoms, biochemical laboratory, radiologic, and intraoperative findings, extent of surgical resection. histologic findings, local recurrence and distant metastasis were analysed in 4 patients diagnosed pathologically as a parathyroid carcinoma after operation from 1992 to 1998.

Mean age was 46.7 years (33~51 years) and male to female ratio was 1:3. Neck mass was found in 3 patients, multiple bone pain in 3 patients and renal stone in 1 patient. One case has suffered from chronic renal failure for 19 years. Although preoperative laboratory evaluations showed the aspects of hyperparathyroidsm in all the cases, mean serum calcium level was 11.1 mg/dl (10.5~12.0 mg/ dl), slightly elevated. Laboratory values after surgery were within the normal range in 3 cases. However, in one case with chronic renal failure, serum PTH levels, serially checked, were above the normal range. Any of imaging methods failed to suggest a parathyroid carcinoma preoperatively. Parathyroid adenoma was suspected in 2 cases, thyroid cancer in the other cases before surgery. The extent of resection was radical resection of parathyroid lesion with more than node dissection and in 2 cases, the resection of recurrent laryngeal nerve or strap muscles was added. During followup period, any local or systemic recurrence were not evident in all the cases.

Although functioning parathyroid carcinoma is a rare disease and its preoperative diagnosis, in general, cannot easily be made, the understanding of characteristic clinical and biochemical feature could help diagnosis at first surgery. Radical resection without remaining residual tumor is most important fo the management of the parathyroid cancer.