CXCL12 and breast carcinoma: From the 42 feline mammary carcinomas evaluated, 6 (14%) samples were classified as CXCR4-negative samples and 36 (86%) as CXCR4-positive samples, with CXCR4-negative mammary carcinoma showing significant higher serum SDF-1 levels (p=0.027, Figure 7B).