[Parathyroid cyst. Case report].

Parathyroid cysts (PCS) are rare, and less than 300 cases have been reported in literature till now. They occur in most cases as a swelling at the lower third of the neck or are identified by means of diagnostic tests performed for other neck diseases. They are rarely symptomatic. They are often confused with thyroid nodules. Rarely give compressive symptoms. PCS are divided into functional (causing hyperparathyroidism, hypercalcemia and hypophosphatemia) and not functional PCS that represent about 10% of PCS. The non functional PCS are considereted true PCS because their wall is lined by secretory epithelium, instead of the functioning ones that are cystic degeneration of parathyroid gland adenomas. The histopathological data suggest the origin of two different variants of PCS. Their diagnosis requires knowledge of the disease and an high suspicion for it. Ultrasound associated with FNA is the first instance investigation. The ultrasound study allows to verify the nature of the cystic lesion and its peripheral vasculature, whereas FNA can observe the macroscopic characteristics of the liquid sample (clear liquid called "water from rocks") and to dose the levels of PTH and C-terminal/mid-region of PTH itself. The dose of intracystc PTH is the universally accepted method for diagnosis of PCS. The first treatment is the aspiration FNA, which can be curative, but recurrences can be treated surgically. Here is a case of PCS, which we observed in June 2009.