Type AB Thymoma
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![Mediastinum_Thymoma_TypeAB_10B.jpg](/slides-13/slides/Mediastinum_Thymoma_TypeAB_10B.jpg)
Comments:
When lymphocytes are too numerous to count in a spindle cell thymoma OR the lymphocytes are arranged in dense clusters OR moderate infiltrate of lymphocytes is seen >10% of the tumor area, such cases are best classified as type AB thymomas. Type A thymomas (spindle cell thymomas) have no or very few (easily countable) lymphocytes.