Immunohistochemical analysis of CXCR4 expression in feline mammary carcinomas. Panel A. Representative primary feline carcinoma showing a high number of neoplastic cells with moderate to intense cytoplasmic positivity for CXCR4. (Bar 25 μm). Panel B. Primary tubulopapillary carcinoma: a poorly differentiated area with low number of positive neoplastic cells showing a weak immunoreactivity for CXCR4. (Bar 25 μm). Panel C. Lymph node metastasis of the feline mammary carcinoma showed in Panel B. Metastatic cells show a marked immunoreaction for CXCR4 if compared with the corresponding primary lesion. (Bar 25 μm). Original magnification 40×.