RESUMEN
Ectopic thymic tissue in the neck is rarely reported in medical literature. Being uncommon, they are rarely included in the clinical diagnosis of cervical cystic masses and are misdiagnosed by surgeons as branchial cysts, lymphatic malformations, epidermoid cysts, dermoid cysts or thyroglossal cysts, lymphadenitis or neoplastic masses. Although it is rare, cervical thymic cyst should be considered in the differential diagnosis of a lateral cystic neck mass. Here we report a rare case of thymic cyst in a young 15-year-old male child on the left side of the neck. Histopathology of the excised cyst revealed thymic tissue composed of prominent Hassall's corpuscles, cholesterol clefts, lymphoid aggregates and cyst lined by cuboidal and squamous cells.