Prominent Thymus

  • Etiology: Normal variant of increased size and weight of thymus with preservation of normal microscopic features
  • Imaging CXR: Enlarged lobes of thymus
  • Imaging US: Normal thymus can be confirmed which shows characteristic starry sky or dot-dash appearance of thymus
  • DDX: Anterior mediastinal tumor
    — Thymus is soft and is displaced by surrounding structures
    — Anterior mediastinal tumor is hard and displaces surrounding structures
  • Complications:
  • Treatment:
  • Clinical:

Radiology Cases of Prominent Thymus

Radiology Cases of Prominent Thymus in Neonate

CXR of a prominent thymus
CXR AP+lateral shows an anterior mediastinal mass without a thymic wave or thymic sail sign that was confirmed on US to be normal thymic tissue.
CXR of a prominent thymus
CXR AP (left) shows a mass projecting over the right superior mediastinum and right superior heart. CXR lateral (right) shows the mass to be in the anterior mediastinum.

Radiology Cases of Prominent Thymus in Infant

CXR of prominent thymus in inspiration and expiration
Inspiratory CXR AP (left) shows an enlarged mediastinal silhouette with a normal heart size while the pulmonary vascularity is normal and the lungs are clear. Expiratory CXR AP (right) shows an even more enlarged mediastinal silhouette with a now enlarged appearing heart.

Radiology Cases of Prominent Thymus in Preschooler

CT of a prominent thymus gland
Axial CT without contrast of the chest shows a prominent thymus gland.

Radiology Cases of Prominent Thymus in School Ager

CXR and CT of prominent thymus
CXR AP (above) shows an abnormal soft tissue density to the left of the spine in the left suprahilar region. Axial CT with contrast of the chest (below) shows in the anterior mediastinum an enlarged thymus which is homogenous in appearance and without any focal lesions.