A mediastinal cyst measuring 6 cm was removed by manubriotomy in a 66-
year-old woman. This patient had no clinical or biological evidence of
hyperparathyroidism. The cyst was close to the thymus and compressed
the innominate venous trunk. It contained a clear fluid. Normal parath
yroid tissue was present in the capsular wall that was fibrous and par
tially calcified. This cysts are rare and their mediastinal localizati
on is exceptional.