Our study is the first to identify a region on chromosome arm 18p likely to contain a putative TSG involved in breast oncogenesis, and to show that this TSG may be L3MBTL4. We did not exclude the existence of other potential 18p TSGs, some of which could explain the aggressive phenotype of breast tumors with 18p loss. The gene discussed is L3MBTL4; the disease is breast neoplasm.