FOXR2 and brain neoplasm: These data indicate that NB-FOXR2 tumors originate from LHX6+/DLX+ interneuron lineages, a lineage of origin distinct from that of other FOXR2-driven brain tumors, highlight the susceptibility of ventral telencephalon–derived interneurons to FOXR2-driven oncogenesis, and suggest that FOXR2-induced activation of glial programs may explain the mixed neuronal and oligodendroglial features in these tumors.