Thymus cancers are rare. The thymus is made up of various cells, each which has the ability to develop into different types of cancer.
Epithelial cells give the thymus its structure and shape. Thymomas and thymic carcinomas, develop from these cells
Lymphocytes make up most of the rest of the thymus. Whether in the thymus or other parts of the body these immune system cells can develop into cancers such as Hodgkin disease and non-Hodgkin lymphoma.
Kuchitsky cells, or neuroendocrine cells, are far less common cells that typically release certain hormones. These cells can give rise to cancers called carcinoid tumors.
Our focus from here on out will be on the Epithelial cells, which as stated above are the cells that give rise to thymomas and thymic carcinomas. More recently, thanks to molecular studies in these tumors, it has become clear that the genetics of thymomas and thymic carcinomas are different, although the distinction between thymomas (especially B3 thymomas) and thymic carcinomas may be somewhat blurred.
When it comes to thymus cancer, it is important to be able to differentiate, once diagnosed, if your cancer is a Thymoma or a Thymic Carcinoma, this will change the trajectory of your treatment, the specialists you will want to see.
Keep in mind that the classification of these tumors may not be easy when it is based on small biopsies, because combined forms are not uncommon.
Thymomas are classified into A, AB, B1, B2 and B3 thymomas (based on the type of cells present in the tumor) and display a relatively conserved structure of the thymus gland. In general thymomas are less aggressive, more treatable and oftentimes associated with autoimmune diseases, in particular Myasthenia Gravis. Thymoma cells tend to grow very slowly, and it’s rare for them to spread to other parts of the body.
Thymic carcinomas have been traditionally considered to be the most dangerous and aggressive type of thymomas (previously called type C thymoma). Under the microscope it contains cells that look very abnormal and they may no longer even look like thymus cells. Thymic carcinoma cells grow very rapidly and tend to spread through the body. Oftentimes by the time thymic carcinoma is diagnosed, there is a significant chance that it will have already metastasized. Therefore, thymic carcinoma generally requires complex treatments.
It is also important to note that thymomas are more common than thymic carcinomas.