9-1-2-Thymic tumors

1-Thymic gland disappear after the year of 21 years old.

2-Normal variant is to see thymic tissue in the neck by sagital MRI.

3-Most important lesions are thymoma and thymic lymphoma.

4-Thymoma:

-Types: invasive and non invasive thymoma.

-35% of the patient with thymoma have myethenia gravis.

-15% of the patients with Myethenia gravis have thymoma.

-Thymic gland is sail in appearance with borders convex to outside, as the child grow the edges start to become flat then concave. If you see it in older child with convex borders to outside, this means pathology.

-If the patient does not have history of lymphoma, we report that the mass seen in the anterior mediastinum is thymoma after exclusion of the retrosternal goiter.

But if the patient has a history of lymphoma, we report this mass as thymic lymphoma.

So if we have an anterior mediastinal mass, look first if it is connected to the neck by a thyroid goiter or not, If it is connected, diagnose it as retrosternal goiter. If it is not connected, ask about lymphoma history or presence of other lesions in the spleen or lymph nodes, if present, diagnose thymic lymphoma, if not present diagnose thymoma.

-How to differentiate between thymic lymphoma and thymoma in adults or children:

By floating vessels sign, in which in case of thymoma, the vessels will be displaced posteriorly, while in case of lymphoma, the vessels will be seen floating inside the mass.

-Invasive thymoma causes encasement of the vessels or airways such as SVC.

Floating vessel sign

In thymoma, the vessels are displaced posteriorly