Although several members of the NKX2 homeobox family have been involved in the development of solid tumours and T-cell leukaemias8, 21, ectopic expression of NKX2-3 in mouse B lymphocytes induced the development of clonal B-cell neoplasms closely mirroring the spectrum of human NKX2-3-expressing lymphomas. This evidence concerns the gene NKX2-3 and B-cell neoplasm.