Figure 4. (A & B) Sections show tumors with extensive areas of necrosis. IHC for PD-L1 shows crisp membranous positivity in the tumor cells in the viable areas (black arrows in A, IHC X100). However, the necrotic foci show diffuse positivity for PD-L1, the intensity, and percentage of which are difficult to assess (red arrows in A and B). (B) High power view showing tumor cells with diffuse PD-L1 positivity (red arrows), entrapped in the necrotic debris (IHC X400).
PD-L1: Programmed death-ligand 1; IHC: Immunohistochemistry.