Ultrasound of the parotid gland.

Five cases of parotid gland masses were studied by ultrasound. Only retention cysts and true cysts of the parotid gland appear sonolucent at low and high gain settings. Benign and malignant tumor present as solid masses except for the Warthin's tumor which is sonolucent at lower gain settings but has a lattice of internal echoes at higher gain settings.