# Ectopic Thymus in Paediatric Thyroid: Support for Conservative Management

## TL;DR

A young child had a benign thymus tissue in her thyroid, which was correctly identified using ultrasound, avoiding unnecessary invasive procedures.

## Contribution

This case supports the use of ultrasound for diagnosing ectopic thymus in the thyroid without needing a biopsy.

## Key findings

- Ultrasound can distinguish ectopic thymus from thyroid malignancy.
- Ectopic thymus in the thyroid is a benign condition that does not require invasive investigation.
- Conservative management is feasible based on ultrasound findings.

## Abstract

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.