Echogenic floating spherules as a sonographic sign of cystic teratoma of mediastinum: correlation with CT and pathologic findings

Echogenic mobile spherules in a cyst as an ultrasound finding in cystic mediastinal teratoma

Mature teratomas are the most common mediastinal germ cell tumor. They are mostly cystic. They are usually asymptomatic and diagnosed incidentally on chest X-ray or CT scan. The diagnosis of teratoma is usually confirmed by CT scan. It shows variable combination of fat, fluid, soft tissue component, and calcification. Ultrasound, a cheap and widely available imaging modality, also provides valuable characteristic appearances of mediastinal teratomas. We present a case of mediastinal cystic teratoma showing characteristic echogenic mobile spherules in the cyst and its brief discussion.

Mature mediastinal teratoma: sonographic imaging patterns and pathologic correlation

OBJECTIVE

To characterize the sonographic patterns of teratomas located within the mediastinum and to correlate them with pathologic findings, because there have been few reports concerning the application of sonography in the diagnosis of mediastinal teratoma.

METHODS

Over a 9-year period, we carried out an image analysis of the sonographic findings of 28 mediastinal teratomas whose diagnoses were proved surgically.

RESULTS

Sonography showed that 18 patients had a complex mass of heterogeneous echogenicity, including regional bright echoes (n = 12), acoustic shadows (n = 8), hyperechoic lines and dots (n = 7), soft tissue septa (n = 9), dermoid plugs (n = 6), and hypoechoic areas (n = 11). This type of mediastinal teratoma revealed, in pathologic findings, varying combinations of fat, sebaceous and mucinous materials, hair, mineralized elements, and multiple compartments. Eight patients had a homogeneous hyperechoic mass, and the 2 remaining patients had floating spherules within a cystic mass. Pathologically, the homogeneous mass mainly contained hair and sebaceous material. The floating spherules were also composed of sebaceous tissue and were above the fluid of the cyst.

CONCLUSIONS

On the basis of the evaluation of the sonographic and pathologic findings, we described 3 major patterns of mediastinal teratoma: a complex mass of heterogeneous echogenicity, homogeneous high echogenicity within a solid mass, and floating spherules within a cystic mass. Thus, sonography can improve the diagnosis of mediastinal teratoma. However, additional prospective studies are needed to test the sensitivity and specificity of these sonographic patterns in the diagnosis of mediastinal teratoma.