IMMUNOHISTOCHEMICAL EVALUATION OF P62 IN CANINE MAMMARY TUMORS

Introduction: P62 is a ubiquitin-binding scaffold protein considered the crossroad molecule of autophagy and apoptosis. In veterinary medicine, the role of p62 in tumors is poorly understood. The aim of this study is to evaluate the immunohistochemical expression of p62 in normal mammary tissue, in adenomas and carcinomas of the dog. Materials and Methods: The immunohistochemical analysis were performed on thirty-six mammary tumors classified according to WHO and eight normal mammary tissues. Regional lymph nodes were analyzed when present. Results: All normal tissues exhibited a strong, homogeneous positivity. Almost all epithelial cells showed a brown granular stain in the cytoplasm while the nucleus was negative. Only 5% of myoepithelial cells were immunostained and the stroma was always negative. In all adenomas p62 immunostaining was enough intense but the percentage of epithelial positive cells was lower (65%). In malignant tumors, the immunoreaction appeared heterogeneous both between samples and within the same sample. 19 carcinomas (68%) showed small areas strongly positive close to others hardly negative, while 9 (32%) exhibited a diffuse weak stain. Metastatic cells in lymph nodes were p62 positive in 50% of cases. Conclusions: These data could suggest a negative correlation between p62 expression and neoplastic progression. To date, as the paucity of cases examined and the complex role of p62 in autophagy and apoptosis, we believe that is not possible to consider p62 a progression marker. In the future will be interesting to compare these results with data obtained from breast cancer studies.