Ectopic Thymus in Paediatric Thyroid: Support for Conservative Management.

We present a case of conservatively managed intrathyroidal thymic tissue in a 3.5-year-old girl, who had an ultrasound for a midline swelling that was consistent with a dermoid cyst, proven by operative specimen pathology. An incidental finding was that of thymic tissue within the thyroid, the ultrasound characteristics of which enable differentiation from thyroid malignancy, enabling a confident diagnosis of this benign, asymptomatic condition. Thus, rather than proceeding to invasive investigations, detailed ultrasound analysis obviates the need for thyroid biopsy. The features that enable malignancy to be excluded are discussed.