CXCR4 score in feline mammary carcinomas. Box plots represent the distribution of CXCR4 score in different feline mammary carcinoma histological types. A statistically significant relationship (Pearson's Chi sqr. test) was observed between the increase of CXCR4 scores from normal to benign, malignant and metastatic mammary tissues. Each box shows the median, quartiles, and extreme values within a group.