Upon examination of four IDH-mutant tumors with NE and CE samples available (Fig. 2b), we identified two IDH-mutant tumors exhibiting heterogeneous EGFR alteration, including the presence of a low allele frequency (2%) EGFR A289V gain-of-function mutation unique to the NE region in one patient tumor (Fig. 2b). The gene discussed is EGFR; the disease is neoplasm.