The S100A4 ELISA is able to detect S100A4 protein in human plasma and serum samples. S100A4 is a member of the S100 family. To date, the family consists of 22 members. S100 proteins are low molecular weight calcium binding proteins. The proteins consist of 2 calcium binding EF-hands located on the termini flanked by hydrophobic hinge regions. Calcium ions acts as a global second messenger involved in the regulation of many aspects of cell function. S100 proteins are involved in sensing and transforming calcium signals to downstream cellular responses. S100 family members are located in the cytoplasm and/or nucleus of a wide range of cell types and involved in the regulation of cellular processes such as cell cycle progression and differentiation and inflammatory responses. Several S100 members have been found to act as cytokines in inflammation, particularly in autoimmune skin conditions such as psoriasis. S100A4 may function in motility, invasion, and tubulin polymerization. Chromosomal rearrangements and altered S100A4 gene expression have been implicated in tumor metastasis. Studies have shown that S100A4 is involved tumor progression and metastasis in various malignant tumors. It is suggested that S100A4 serves as a promising candidate biomarker for early diagnosis and prediction of metastasis in several types of cancer.