ID2 and neoplasm: Here, we report the identification of inhibitor of DNA binding 2 (ID2, also known as inhibitor of differentiation 2), a helix-loop-helix (HLH) protein and transcriptional regulator, as well as its interacting transcriptional partner, ETS proto-oncogene 2, transcription factor (ETS2) as involved in the acquisition of the microglial reactive state associated with tumour-trophic functions.