A 26-year old woman was admitted with clinical and laboratory signs and symptoms of chronic infection and multiple cervical lymphadenopathy, whose pathological studies disclosed a non-specific inflammatory reaction. Anti-tuberculosis treatment was then started, with no significant improvement. Chest CT scans was compatible with a mediastinial tumor and RMN studies revealed the presence of an infected bronchogenic cyst, which was surgically and successfully removed with complete disappearance of the infection. The authors conclude by enhancing the fact that bronchogenic cysts may course with diverse clinical manifestations and should be included in differential diagnosis of mediastinal tumors.