대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Dermoid Cyst (Mature cystic teratoma)

Radiologic Findings

Chest radiograph shows a well-defined mass in the right anterior mediastinum.
Contrast-enhanced CT scan shows a well-demarcated cystic mass in the anterior mediastinum.
The wall of the mass is thick and well enhanced.

Pathology:
Specimen photographs after mass excision show a well-demarcated cyst with yellow internal contents.

Brief Review

The majority of mediastinal teratomas are cystic and benign; the relatively uncommon solid forms are usually malignant. Pathologically, tumors can be divided into three types including mature teratomas, immature teratomas, and teratomas with malignant transformation.

Mature cystic teratomas are found at all ages, but particularly in adolescents and young adults, with females slightly outnumbering males. They usually consist predominantly of ectodermal elements-hence the expression "dermoid cyst"-such as skin, sebaceous material, hair, and calcification along with smooth muscle and respiratory epithelium. In most series half the cases are asymptomatic and diagnosed incidentally on chest radiography or CT. Symptoms are caused by local compression, rupture, or infection. The most common symptoms are chest pain, a cough that is usually productive, dyspnea, and fever.

Mature cystic teratomas usually produce a well-defined, rounded or lobulated mass in anterior mediastinum in front of the roots of the aorta and main pulmonary artery, but a few are found in the posterior mediastinum or lung. Benign cysts grow slowly, but rapid increase in size may occur because of hemorrhage. Alternatively, they may rupture into the bronchial tree in which case air may enter the cyst and be visible on imaging examinations. Rarely the cyst may rupture into the pericardium or pleura, in which case a fat-fluid level may be visible in the pleural space. Most teratomas project mainly to one side of the midline, sometimes markedly so. Calcification, ossification, or even teeth may be visible on a chest radiograph, and occasionally, sufficient fat is present to be detectable radiographically.

The findings at CT are variable. Water density in the cystic component is common, and fat density is seen in one fourth to one half of the patients. A fat-fluid level may be seen, or fat and fluid may be more immediately mixed. A definite cyst wall, which may show curvilinear calcification, is often visible. The combination of a large anterior mediastinal mass, which is wholly or predominantly composed of a cyst, with a well-defined wall is highly suggestive of a cystic teratoma. With calcification in the wall of the cyst or small spherical or irregular calcifications within the mass, cystic teratoma is even more likely. Unequivocal fat within the mass, particularly a fat-fluid level, makes this diagnosis certain.

References

1. Amstrong P. Mediastinal and Hilar Disorders. In: Amstrong P, Wilson AG, Dee P, Hansell DM eds. Imaging of diseases of the chest. 2nd ed. Mosby 1995:732-734.
2. Fraser RS, Pare JAP, Fraser RG, Pare PD. Diseases of the mediastinum. In: Fraser RS, Pare JAP, Fraser RG, Pare PD, eds. Synopsis of diseases of the chest. 2nd ed. Philadelphia: Saunders 1994:912-913.

Keywords

Mediastinum, Benign tumor,