We analyzed lactoferrin expression in 78 samples from patients with sporadic breast cancer and found 31/78 negative for mRNA expression. Similar results were obtained by immuno-histochemical localization of the lactoferrin protein. We did not find relationship between lactoferrin expression and clinical parameters. We investigated for the absent lactoferrin expression in some cases of breast cancer. In 68 of the samples analyzed, we found an inverse correlation between estrogen receptor expression and lactoferrin expression (P < 0,0001), thus indicating that regulation by the estrogen receptor is not the main element responsible for the expression of lactoferrin in breast cancer. Analysis of methylation of the lactoferrin genomic DNA extracted from the same patients revealed that the degree of methylation does not explain the observed absence of lactoferrin. The 937 bp lactoferrin promoter was investigated for possible mutations. By single-strand conformation polymorphism analysis one polymorphic site was found and characterized.