Abstract
Benign cystic lesions such as cystic hygroma commonly manifest as progressively increasing swelling in the neck with or without compression effects. Rarely, they present with sudden respiratory distress in instances such as infection or haematoma resulting in a sudden increase in the size of the tumour. We present a seven month old child with sudden onset respiratory distress without any obvious neck swelling. The chest X ray findings correlated with the history and were suggestive of right upper lobe pneumonia that leads to a wrong diagnosis of aspiration pneumonia. However, presence of a deviated trachea in the neck raised a suspicion of possible mass. Computed tomogram showed a large cystic mass in the right upper mediastinum with tracheal collapse. We caution intensivists and paediatricians that sudden respiratory distress in infants in the absence of obvious neck swelling does not rule out possibility of intrathoracic tumour.