Type AB Thymoma : Microscopic

Type AB thymoma is composed of lymphocyte-poor type A areas containing neoplastic spindle epithelial cells (upper left) and a more lymphocyte-rich type B component (lower right). The two areas may be sharply demarcated (as seen in this case) or may be intermixed. Type AB thymoma is one of the most common subtypes and makes up about 28% of all thymomas.