9-1-3-Mediastinal germ cell tumors(terato dermoid)

1-Mainly diagnosed by presence of fat (presence of fat is very important than presence of calcium).

2-It is composed of fat, calcium, and shows cystic changes.

3-As most of mediastinal lesions, it characterized by asymptomatic state or the patient may complaint of compression symptoms.

4-It characterized radiologically by presence on both sides of the anterior mediastinum but with big component on one side and small component on the other side.

5-Presence of hyper dense structures in CT represent calcium, while presence of hyper intense signal in MRI T1 represent fat denoting that the lesion is teratodermoid.

6-A lesion seen crossing the midline and represented on both sides of the mediastinum is a definite sign that this lesion is a mediastinal one and not a pulmonary lesion.

7-Malignant teratoma shows invasion of mediastinal structures and multiple or single pulmonary metastases.

8-If you have a patient with a big mass showing cystic component in addition to single or multiple pulmonary nodules which represent pulmonary metastases, search first for the origin of this mass, is it pulmonary or mediastinal, if it is pulmonary in origin, your diagnosis should be a bronchogenic carcinoma with lung metastases. But if the origin of this mass is mediastinal, look if this mass is connected by another one in the neck or not, if it is connected, your diagnosis will be cancer thyroid. But if it is not connected, look into the mass itself if it contains a true cystic component with well defined wall or not, if it contains this component, your diagnosis will be malignant teratoma even if there is no fat or calcium component, but if it contains necrotic component ( cystic area without definite well defined wall ), the lesion will be thymoma.