Tumor NOS2 expression was moderately to strongly expressed in 70% of all (ER+ and ER−) tumors, whereas only a few tumors (10%–20%) showed marked NOS2 expression in infiltrating CD11b+ immune cells, implicating the tumor epithelium as the major source of NOS2-derived NO in breast tumors (4). This evidence concerns the gene ESR1 and neoplasm.