Parathyroid cysts. Medical diagnosis and management.

Two patients had asymptomatic neck masses that proved to be cystic. In each case, the lesions resolved after needle aspiration of 25 ml of clear, colorless fluid. Serum thyroid indexes and calcium levels were normal. Cyst fluid parathyroid hormone (PTH) levels were 0.56 and 1.50 ng/ml, respectively. The serum PTH level in case 1, determined at the same time, was less than 0.05 ng/ml (normal, 0 to 0.3 ng/ml). These observations indicate that (1) clear, colorless cyst fluid may indicate a parathyroid cyst, (2) serum and cyst fluid PTH levels can confirm the diagnosis, and (3) needle aspiration may be appropriate therapy for the benign, nonfunctioning parathyroid cyst.