IDH2 and sinonasal undifferentiated carcinoma: IDH mutations have been firstly identified in colorectal cancer and glioblastoma [36,37] and lately associated with the occurrence of acute myeloid leukemia (AML) (~20% of cases) [38,39,40,41]; angioimmunoblastic T lymphoma (32%); and various solid tumors including low-grade glioma and secondary glioblastoma (80%) [10,42,43], cholangiocarcinoma (20%) [44,45], chondrosarcoma (50–80%) [46], and sinonasal undifferentiated carcinoma (SNUC) (49–82%) [47,48] (Figure 2 and Table 1).