Thymic rebound hyperplasia

Thymic rebound hyperplasia is considered a from of true thymic hyperplasia.

Pathology

In periods of bodily stress the thymus may acutely shrink to 40% of its original volume (depending on the severity and duration of the stress). During the recovery phase it can grow back to its original size or even larger (up to 50% larger). This "rebound effect" is known as thymic rebound hyperplasia. It typically takes the thymus 9 months to return to its original size .

Examples of acute stress events that can trigger thymic atrophy and later rebound include:

  • pneumonia
  • corticosteroid therapy
  • radiation therapy
  • chemotherapy
  • surgery
  • burns
  • post-chemotherapy 10-25% will undergo rebound hyperplasia, usually occurring within 2 years of treatment    

Rebound hyperplasia is typically seen in children, but can also occur in adults .

Radiographic features

CT

Thymic rebound hyperplasia typically shows diffuse enlargement, a fine mixture of fat and lymphoid tissue, a smooth contour, and normal vessels .

PET

The normal thymus is typically barely visible on PET. However, in rebound hyperplasia it show intense FDG uptake. This can lead to confusion, and misdiagnosis of lymphoma .

See also

Siehe auch: