A case of dermoid cyst ruptured into the lung.

Ruptured cystic teratomas (dermoid cysts) are rare and always symptomatic, presenting as haemothorax, pleural effusion or pericardial effusion. We present an extremely rare case of a 45-year-old woman who, during a routine health assessment was noted to have a well-defined anterior mediastinal tumour with peripheral ground glass opacity on chest CT. The patient was asymptomatic. She underwent video-assisted thoracoscopic surgery and a ruptured dermoid cyst was observed and the contents had infiltrated into the right pulmonary parenchyma. There were no complications and no evidence of recurrence 10 months later. Despite most cystic teratomas being asymptomatic and benign, rupture into the pulmonary parenchyma may induce further damage, for which emergency surgical intervention is always necessary.