The major protein essential for the uptake of iron is transferrin receptor (TfR), encoded by TFRC, which is found primarily as a homodimer. TfR is a type II transmembrane glycoprotein that is endocytosed from the cell membrane after binding iron with transferrin (Tf), a serum iron carrier protein. TfR was found to affect many aspects of tumorigenesis, such as cancer cell proliferation, migration, invasion, metastasis and apoptosis. TfR expression was consistent with the asthma severity index, especially the proinflammatory M1 macrophage phenotype. TfR expression may be a good marker to indicate asthma severity. Increased TfR expression and decreased methylation levels of TfR were strongly correlated with multiple clinicopathological parameters. Elevated TfR expression was associated with a poor survival rate in BC patients. TfR is a new independent prognostic biomarker and a potential target for immunotherapy in BC.