Undescended thymus presenting as midline neck swelling

A seven month male child presented with midline neck swelling which was visible in the suprasternal notch when the child cried. Computed tomography revealed that it was thymic tissue (solid). There was no thymic tissue in the normal position. Undesended thymus or ectopic thymus is a rare cause of neck mass. Solid type as seen in this case constitute 10% of ectopic thymic tissue ,90% being of cystic variety. Caution should be exercised in excision of such masses as they may be the only thymic tissue.