An unusual case of malignant invasive thymomaByJohn E. Cho, MD,Nora Ostrzega, MD,Nader Kamangar, MDJanuary 13th 2010Malignant thymoma is an indolent tumor arising from the thymic epithelial cells located in the anterior mediastinum. These tumor cells spread via regional metastasis or invade surrounding structures, including the pleural space.