P- and E-cadherin expression by immunohistochemistry (IHQ) and by double-label immunofluorescence (DIF) in feline mammary tissue. A. P-cadherin immunohistochemistry (IHQ) - (a) Normal mammary gland with strong expression of P-cadherin by myoepithelial cells and lack of immunoreactivity in luminal epithelial cells. IHC. x400; (b) Strong P-cadherin expression in high atypical neoplastic cells from a grade III tubulopapillary carcinoma. IHC. x200; (c) Neoplastic intravascular embolus showing strong P-cadherin expression. IHC. x400; (d) Lymph node metastases showing P-cadherin expression by neoplastic cells. IHC. x100. B. P- and E-cadherin double-label immunofluorescence (DIF) - (a) Normal mammary gland tissue with P-cadherin in myoepithelial cells (green colour) and E-cadherin in luminal epithelial cells (red colour). DIF. x200; (b) Tubulopapillary carcinoma with tumour cell populations co-expressing P-cadherin and E-cadherin (yellow colour). DIF. x200; (c) Neoplastic intravascular embolus. DIF. x200. and (d) lymph node metastatic cells. DIF. x200. with a pattern of expression similar to primary malignant neoplasia, with tumour cell populations co-expressing P-cadherin and E-cadherin (yellow colour).