Since the cause and defects underlying thymoma development have not been elucidated, it is only a speculation that thymic tumor microenvironment can cause aberrant maturation of autoreactive T cells; however, oligoclonal expansions of bone marrow resident beta variable region 8-CD8+T cells have been reported in some cases [71], but no corresponding population was found in the periphery. Here, CD8A is linked to thymoma.