Needle aspiration of nonfunctioning parathyroid cysts.

Parathyroid cysts, appearing as thyroid masses, have been previously diagnosed at operation or by permanent histologic specimens. With the advent of ultrasound and fine-needle biopsies, these very rare cysts can now be diagnosed by needle aspiration. The pearly clear fluid of a parathyroid cyst contrasts with the sanguineous or even chocolate-brown fluid of a thyroid cyst. The high parathyroid hormone (PTH) level of the fluid confirms the diagnosis, and a blood calcium level determines its function or nonfunction in the patients. Of our seven nonfunctioning parathyroid cysts, the first three were diagnosed by operation and the other four by needle aspirations. The PTH determination ranged from 20,000 to 42,000 pg/mL. We suggest that needle aspiration, rather than operation, be the treatment of choice.