- Normal thymus
- Prominent thymus
- Thymus involution / Thymus rebound
- Cervical thymus
- Absent thymus
- Leukemia
- Lymphoma
- Thymoma
- Thymic cyst
- Lymphatic malformation
- Teratoma
Approach to the differential diagnosis of thymus mass:
- On CXR look for thymic wave sign + thymic sail sign to determine whether you are looking at a normal thymus
- US is a great way to differentiate a prominent thymus with the starry sky appearance of normal thymus from a thymus mass
- If the thymus appears absent in a newborn, consider DiGeorge syndrome
- Thymic rebound must be differentiated from recurrent tumor in anterior mediastinal mass patients (leukemia / lymphoma) who have finished their chemotherapy
- Fat and calcium in a thymus mass usually indicates teratoma, fluid in a thymus mass usually indicates thymic cyst or lymphatic malformation, a solid homogenous thymus mass is usually a thymoma
Pediatric Imaging 