Pitfalls and mimics : the many facets of normal paediatric thymus

Abstract

The thymus is a lymphatic organ that was often thought of as an organ of mystery by the ancient Greeks. A soft, pliable lymphatic organ positioned in the anterior superior mediastinum, it does not compress or displace the adjacent structures. It is disproportionately larger in the paediatric population and then gradually regresses to ‘hide’ in the mediastinum as the child advances into puberty. It regresses in size under conditions of stress and may be absent in various congenital abnormalities such as DiGeorge syndrome and conditions of stress. The thymus appears in a variety of shapes and sizes on a paediatric chest radiograph and at times may be misinterpreted as pathology. This article describes the normal thymus as it appears on paediatric radiography, and addresses mimickers.