Spontaneously Regressing Thymic Cyst

Thymic cysts are uncommon lesions, constituting 1- 3% of all mediastinal masses. Most of these cysts are asymptomatic and found incidentally through routine chest roentgenograms. Our patient was asymptomatic, and a routine chest x-ray revealed mediastinal widening. A mediastinal mass, 6x4 cm in dimension, was detected by computed tomography. The lesion was hypodense, well defined, and cystic in nature. Magnetic resonance imaging of the thorax revealed a typical cyst expanding from the rudimentary thymus tissue. Although total excision of the cyst is the preferred treatment modality in these patients, close radiological follow-up of our patient revealed total remission. In conclusion, asymptomatic thymic cysts can be radiologically monitored and spontaneous remission can be observed.