fig5

Figure 5. Type B1 thymoma: (A) scanning magnification shows the appearance of a “blue cell tumor” due to the massive amounts of small lymphocytes, and the characteristic lobulation separated by broad fibrous bands (2×); (B) area of “medullary” differentiation is seen in a B1 thymoma, characterized by a rounded zone that looks paler than the surrounding tissue owing to a decrease in the number of small lymphocytes (20×).