The objective of this study was to compare levels of four elements (zinc, copper, selenium, and iron) in the serum and tissue of 68 breast tumor patients (benign and malignant), from a teaching hospital in central Taiwan. Samples of normal tissue (5 cm away from tumor) were also taken from patients with malignant tumors. Only serum was taken from the 25 healthy persons in the control group. Results showed that Zn, Cu, Se, Fe, Cu/Zn, Cu/Se, and Cu/Fe were present in different amounts in the serum of each of the three groups. Zn and Se levels were lower in the serum of the two tumor groups compared to the control group. In tissue samples, Zn, Cu, Se, and Fe concentrations were different in each of the three groups. The malignant tissue had the highest levels of all four elements. In advanced-stage malignant tumors, levels of Cu and the ratios of Cu/Fe and Cu/Zn (in both serum and tissue) were highest. The ratios of serum Cu/Zn, Cu/Fe, and Cu/Se were also higher in malignant patients. The cutoff value of serum Cu/Zn was 1.2 (sensitivity and specificity were both 100%). The Cu/Zn ratio was highest in the advanced stages of cancer and was a better diagnostic tool for breast cancer than Cu/Se and Cu/Fe. The authors suggest that change of trace elements in serum and tissue might be useful and significant as biomarkers involving the initial plastic process.