In veterinary medicine, knowledge of the role of p62 in tumors is still limited, therefore, the purpose of this study is to evaluate the immunohistochemical expression of p62 in feline mammary carcinoma with different degrees of differentiation and in non-neoplastic mammary glands to highlight how this protein is expressed and if there is a correlation with the degree of the malignancy of the tumor. The gene discussed is SQSTM1; the disease is neoplasm.