Treatment of a nonfunctioning parathyroid cyst with tetracycline injection.

Parathyroid cysts are uncommon: about 200 cases have been reported. They can be functional (i.e., accompanied by signs of primary hyperparathyroidism), or nonfunctional. Preoperative diagnosis is difficult, although it has become increasingly frequent with the use of ultrasound and fine-needle aspiration biopsy. Fluid of parathyroid cysts is almost invariably watery, colorless, and crystal clear, which should cause clinical suspicion. However, definitive diagnosis relies on the demonstration of high parathyroid hormone (PTH) levels in the fluid. Puncture may cure nonfunctioning cysts, but surgery is indicated when the lesion recurs after several fine-needle aspirations. We report a case of a nonfunctioning parathyroid cyst in a 17-year-old boy, which reappeared after two punctures made 6 months apart. On the third occasion, 1 mL of a sterile tetracycline solution injected into the cyst cured the lesion. Tetracycline and other sclerosants have been recommended as a treatment of recurring thyroid cysts. We suggest that injection of a sclerosant should be considered as an alternative to surgery in recurring, nonfunctional cysts of the parathyroid glands.