[Parathyroid cyst].

Parathyroid cysts are grouped into two: functioning and non-functioning cysts. Most of the functioning cysts result from the cystic degeneration of parathyroid adenoma, while, non-functioning cysts, in many cases, originate from Kürsteiner's canal on the third branchial cleft. It is difficult to differentiate parathyroid from thyroid cysts morphologically. However, the measurement of assay of parathyroid and thyroid hormone in the aspirated fluid enables differentiation. Hypercalcemic crisis occurs frequently in the functioning cysts. Moreover, we propose sclerotherapy as the treatment for the non-functioning cysts.