Cervical thymic cyst is uncommon and usually occurs in the first and second
decades. Cervical thymic cyst after the third decade is so rare that it is
very difficult to diagnose in spite of its typical location. We present a
rare case of cervical thymic cyst in the lower left - anterior of the neck
in a 50-year-old woman. It showed well-defined, anechoic cyst on ultrasonog
raphy and non-enhancing low attenuation mass on CT. A typical anatomic rela
tionship was noted between the mass and carotid sheath.