IDH1 and neoplasm: Figure 1A shows a highly cellular tumor in which microvascular proliferation is evident in the center of the microscopic field. The image in Figure 1B shows the immunohistochemical staining results for IDHR232H, a genetic marker commonly used to identify glioblastomas with IDH mutations. The neoplastic cells are negative for this marker, indicating that they do not carry this specific mutation. Figure 1C,D provide the control, representing a glioblastoma IDH mutant with the same staining as Figure 1A,B.