Thymic cyst: is a correct preoperative diagnosis possible? Report of a case and review of the literature

A case of a giant cervico-mediastinal cyst of thymic origin in an 8-year-ol d child is presented. The cyst was asymptomatic except for deformity due to its size. In spite of several diagnostic approaches like ultrasonography, computed tomography, cyst puncture with biochemical analysis of cyst conten t and direct contrast injection and radiography after emptying of the cyst, the ultimate diagnosis as to the origin of the cyst was not disclosed unti l after operation and histopathological examination of the operative specim en. On a more general basis the diagnostic possibilities and pitfalls are d iscussed. Conclusion: a correct preoperative diagnosis of a thymus cyst is difficult and in many instances impossible even when all diagnostic measure s at hand are utilized, including radiographic methods, computed tomography , magnetic resonance imaging, ultrasonography and biochemical examination o f cyst aspirate and estimation of tumour markers in cyst fluid and serum.