Urokinase plasminogen activator expression in canine malignant mammary tumours by immunohistochemical study

Immunohistochemical expression of urokinase plasminogen activator (uPA) was studied in 37 canine malignant mammary tumours to define the relationship between their histopathological type and grade. In 29 (78.4%) cases, expression of uPA by neoplastic cells was more than 10% and in 34 samples (91.9%) uPA expression by stromal cells (fibroblasts) was more than 10%. The uPA was expressed in epithelial and myoepithelial cells of carcinomas and carcinosarcomas and mesenchymal population of carcinosarcoma, chondrosarcoma, and carcinomas arising in benign tumours. The intensity and percentage of expression of uPA by stromal cells was associated with their histological grade (P < 0.05). However, no significant relationship was detected between uPA expression by neoplastic cells (epithelial, myoepithelial, and mesenchymal cell) and histological grade. Increased expression of uPA by tumour stroma was associated with poor prognostic factors. Stromal expression of uPA could be a prognostic indicator for canine mammary tumours.