Intrathyroidal thymic tissue mimicking a thyroid nodule in a 4-year-old child.

A 4 year-old girl was referred for CT of her neck for suspected submental lymphadenopathy and was found to have an incidental low-attenuation thyroid mass. Subsequent thyroid ultrasound showed a heterogeneous thyroid mass with punctate areas of increased echogenicity. Cytologic examination was consistent with ectopic intrathyroidal thymic nodule. We review the presentation of ectopic thymic tissue, especially in the thyroid gland.