Ectopic cervical thymic tissue: diagnosis by fine needle aspiration.

Cervical thymic masses are congenital lesions that result from aberrant thymic migration during embryogenesis. Although most of these masses are asymptomatic, they may cause debilitating symptoms secondary to encroachment on adjacent aerodigestive structures. Preoperative diagnosis of ectopic thymic tissue is rare; most cases are clinically misinterpreted as branchial cleft remnants or cystic hygromas. Definitive diagnosis has relied on histopathologic examination in nearly all reported cases. However, the invasiveness of open incisional or excisional biopsy carries the risk of surgical and anesthetic complications. Inadvertent surgical thymectomy may result in cell-mediated immune deficiencies in infants and young children. The utility of fine needle aspiration is gaining wider acceptance in the diagnostic evaluation of neck masses. We describe an infant with an asymptomatic cervical thymic mass diagnosed by fine needle aspiration.