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The thymus is a bilobed lymphoid organ sited in the superior mediastinum in adults. It is relatively large at birth and enlarges to a maximal size during puberty when it may extend superiorly to the inferior margin of the thyroid gland within the neck. In adulthood, it regresses as its functional tissue is replaced by fatty connective tissue.
The thymus is thought to have a central role in the development of immune function in adulthood.
Thymic tumours - thymomas - are relatively common mediastinal tumours. Thymic cysts may present widely in throughout the mediastinum.
Thymic is the adjective for items relating to the thymus.