Thymomas and Thymic carcinomas are also classified by the type of cells that make it up. Thymomas are placed into 5 categories created by the World Health Organization.
- Type A thymoma. This is also called spindle cell thymoma or medullary thymoma. The chance of recovery for people with type A thymoma is good. Nearly 100% of people with this type live at least 15 years after diagnosis.
- Type AB thymoma. Also called mixed thymoma, type AB thymoma is similar to type A thymoma. However, type AB thymoma has lymphocytes in the tumor. The chance of recovery for people with type AB thymoma is also good. About 90% of people with this type live at least 15 years after diagnosis.
- Type B1 thymoma. This is also known as lymphocyte-rich thymoma, lymphocytic thymoma, predominantly cortical thymoma, and organoid thymoma. This type of thymoma has many lymphocytes in the tumor, but the cells of the thymus appear healthy. The chance of recovery for people with type B1 thymoma is also good. About 90% of people with this type live at least 20 years after diagnosis.
- Type B2 thymoma. Type B2 thymoma is also known as cortical thymoma and polygonal cell thymoma. This type of thymoma also has many lymphocytes, like type B1 thymoma. However, the thymus cells do not appear healthy. About 60% of people with this type live at least 20 years after diagnosis.
- Type B3 thymoma. Type B3 thymoma is also known as epithelial thymoma, atypical thymoma, squamoid thymoma, and well-differentiated thymic carcinoma. This type of thymoma has few lymphocytes, and the thymus cells look abnormal. Approximately 40% of people with this type live at least 20 years after diagnosis.
Thymic Carcinoma
Thymic carcinomas are not included in the five WHO classifications for Thymoma. Instead, thymic carcinomas are classified by the histological type of cells with which they are composed. The carcinomas are more aggressive in terms of recurrence and metastasizing than thymomas, and are more resistant to chemotherapy.
Some of the histological types are:
1. Keratinizing squamous cell carcinoma
2. Nonkeratinizing squamous cell carcinoma
3. Lymphoepithelioma-like carcinoma
4. Adenosquamous carcinoma
5. Mucoepidermoid carcinoma
6. Clear-cell carcinoma
7. Papillary adenocarcinoma
8. Adenocarcinoma not otherwise specified
9. Basaloid carcinoma
10. Sarcomatoid carcinoma
For Those Who Want to Learn More
You’ll find a little more scientific detail on some of the more common histological type here.