Solid ectopic cervical thymus in neonates with thyroid agenesis.

We report a series of ectopic thymus glands as detected by sonography in infants with thyroid agenesis. The patients were children who underwent nuclear medicine and sonography for congenital hypothyroidism. Of the 12 patients with a diagnosis of thyroid agenesis over a 5-year period, 4 (33%) were shown to have ectopic thymic tissue. Although a cervical ectopic thymus has been previously reported, there is very little discussion of it occurring in conjunction with thyroid agenesis. This case series highlights the importance of recognition of ectopic thymic tissue when examining for thyroid tissue in the setting of congenital hypothyroidism.