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 ancientGreeks. A soft, pliable lymphatic organ positioned in the anterior superior mediastinum, itdoes not compress or displace the adjacent structures. It is disproportionately larger in thepaediatric population and then gradually regresses to ‘hide’ in the mediastinum as the childadvances into puberty. It regresses in size under conditions of stress and may be absent invarious congenital abnormalities such as DiGeorge syndrome and conditions of stress. Thethymus appears in a variety of shapes and sizes on a paediatric chest radiograph and at timesmay be misinterpreted as pathology. This article describes the normal thymus as it appears onpaediatric radiography, and addresses mimickers.