H2AX and neoplasm: In contrast, the expression percentages of γ-H2AX foci in tumor cells of GISTs were not only significantly higher in all NCCN-defined risk levels than those in normal tissue (p < 0.001), but they also exhibited significant stepwise increments from normal tissue to the joint none/very low-/low-risk group (p < 0.001), and from the latter to the joint group of moderate-risk and high-risk cases (p < 0.001), although there were no significant differences when individually comparing the cases at different risk levels within either of the two joint groups (Figure 2G).