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A case of mediastinal mature cystic teratoma (dermoid cyst) presenting with respiratory failure requiring intubation and mechanical ventilation

The University of Oklahoma Health Sciences Center, Oklahoma City, OK

INTRODUCTION: Mediastinal benign teratomas are rare germ cell tumors most commonly found in the anterior mediastinum, and constitute about 3-12% of all mediastinal tumors. They grow slowly and are usually diagnosed incidently, when the patient is still asymptomatic. This is a rare presentation of a mediastinal mature cytstic teratoma(dermoid cyst) presenting with respiratory failure requiring intubation and mechanical ventilation.

CASE PRESENTATION: A 29-year old white female, postpartum day nine, was transferred with a three day history of fever, cough, and increasing dyspnea. Shortly after arrival she developed respiratory failure and was intubated and placed on mechanical ventilation. Physical examination after intubation revealed decreased breath sounds in the left and basilar crackles in the right hemithorax. Routine laboratory tests showed an elevated white blood count of 19,200 with a left shift. Chest roentgenogram demonstrated a peripherally calcified rounded mass occupying a large portion of the left hemithorax, right mediastinal shift, and consolidation of the right hemithorax. Computed tomographic examination showed a 9.9cm x 12.4cm x 12.4cm peripherally calcified cystic mass occyping a majority of the left hemithorax. Several areas of fat attentuation were seen within the lesion. Also demonstrated was a shift of the mediastinum to the right, infiltrative process involving the right hemithorax, atelectasis of the right lower lobe, and a small right pleural effusion. The patient was treated for pneumonia and successfully extubated on day six. Our differential diagnosis was bronchogenic cyst, teratoma, dermoid cyst, and hamartoma. Two days after extubation a posterolateral thoracotomy was performed for histological diagnosis and removal of the cyst. Intraoperatively the cyst was located between the fissure of the left upper and lower lobe and was lateral to and compressing the heart. The cyst was opened and approximately 1.5 liters of turbid fluid was removed. The cyst was then dissected sharply off of the pericardium, pulmonary vessels, and remaining lung parenchyma. The pathology was consistent with a mature cystic teratoma (dermoid cyst) with the pleural cyst wall demonstrating mature epidermis, dermal appendages, pilosebaceous follicles, ciliated epithelia, mucous glands, and smooth muscle. The cystic contents demonstrated lamellated keratin debris and amorphous proteinaceous material consistent with dermoid cyst contents. The patient had an uneventful course after surgery.

DISCUSSIONS: Benign teratomas, also known as teratodermoids, are rare germ cell tumors thought to originate from multipotent embryonic cells near the third branchial cleft. They are divided into 3 groups; epidermoid cysts, dermoid cysts, and teratomas based on their histological appearance. Dermoid cysts contain only ectodermal layer elements, such as skin, tooth, hair and sebaceous glands. They are usually solitary and cystic, but may be multilobulated. About 95% are found in the anterior mediastinum, and mean age at diagnosis is between twenty and thirty years, affecting men and women equally. They grow slowly and are usually diagnosed incidently. About 60% are asymptomatic at the time of diagnosis. The most common symptoms when present are chest pain, dyspnea, and cough. Calcification is one of the most distinctive characteristics of benign teratoms. In this case, the CT scan demonstrated fat density in the lesion and aided in establishing the diagnosis preoperatively.

CONCLUSION: It is extremely rare for an adult with a mediastinal mature cystic teratoma(dermoid cyst)to present with respiratory distress requiring mechanical ventilation. These tumors are generally bengin and surgery is the treatment of choice.

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