The serum concentrations of BDNF (p = 0.008) and MCP-1 (p = 0.025) were significantly higher in BC patients than in healthy controls, and serum concentrations of soluble TREM-1 (p = 0.057) and the soluble sTREM-1/sTREM-2 ratio (p = 0.071) showed a trend to be higher. Here, BDNF is linked to breast cancer.