The thymus is a small gland which is responsible for the production of T-lymphocytes. This organ is larger during the gestation period and can extend into the neck and present different anatomic variants. Ultrasound can identify the thymus via suprasternal, parasternal and sternal approaches, and through the neck when its position is atypical. During adolescence, ultrasound evaluation of the thymus is more difficult due to its involution and reduction in size, and interposition of the lung. The appearance of normal thymus is typical on the ultrasound and produces a unique echo pattern that is less echogenic than the normal thyroid gland with multiple echogenic lines and foci, representing a cross section of either a connective-tissue septum or a blood vessel within a septum. Recognition of normal thymic tissue can be very important in order to avoid unnecessary investigations or surgery of a normal thymus mimicking an abnormal mass.

Keywords: Thymus, Ultrasound, Neck ultrasound