Type B2 Thymoma : Microscopic
At low power, type B2 thymoma has lobular architecture with delicate or thick collagenous bands dividing it into irregularly shaped lobules. The tumor appears basophilic due to abundance of lymphocytes which are predominantly immature T-cells. Within this rich lymphocytic infiltrate, there are polygonal epithelial cells scattered singly or in small clusters. The epithelial cell density is higher than that seen in type B1 thymoma or the normal thymus. This image is from the same case as the previous image. The greater epithelial cell density seen here is beginning to resemble type B3 thymoma.