S100A8 and breast cancer: In light of such studies, the prognostic value of S100A8/9 as a multi-functional protein is yet to be determined, and it provoked us in the present study to evaluate the circulating level of the S100A8/9 heterodimer as a proposed biomarker and CA15-3 as a well-described biomarker in patients with different stages of breast cancer against healthy-matched controls in order to assess the prognostic value of these markers and determine their correlation to the clinicopathological features of patients.