Immune Cells and Immunoglobulin Expression in the Mammary Gland Tumors of Dog

SIMPLE SUMMARY: Among products released by inflammatory cells in the tumor microenvironment, immunoglobulins have been implicated in the pathogenesis and progression of various types of human cancer, but their role in veterinary oncology remains to be fully investigated. This paper aims to describe some of the immune cells inhabiting the tumoral microenvironment and their relationship, if any, with the expression of immunoglobulins. Simple carcinomas of the canine mammary gland showed the highest number of macrophages and B-cells in the so-called invasion areas, along with a strong epithelial immunofluorescence for IgA and IgG. Understanding the crosstalk between the tumor -associated immune cells and the neoplastic epithelium could be pivotal to unravel the pathways that lead to tumor regression or, conversely, promote tumor progression and resistance to chemotherapeutic drugs. ABSTRACT: Inflammatory cells have a role in tumor progression and have prognostic and therapeutic potential. The immunohistochemical expression for Mast Cell Tryptase, Macrophage Marker, CD79a, IgA, IgM and IgG on 43 cases of canine mammary gland lesions was analyzed. In hyperplasia, a few B cells (BCs) and Tumor-Associated Macrophages (TAMs) were observed, while the number of Tumor-Associated Mast Cells (TAMCs) was the highest. In the peritumoral stroma of malignant lesions, low number of TAMCs and a high number of TAMAs and BCs were present. Immune cells of each type were always lower in the intratumoral than peritumoral stroma. Positivity to CD79a was also detected in the epithelial cells of simple and micropapillay carcinomas. Immunoglobulin reactivity was mainly located in the epithelial cells where an intense positivity to IgA and IgG and a weak positivity for IgM were detectable. On the basis of our preliminary results and literature data, we suggest that such cells and molecules could be directly involved in the biology of canine mammary gland tumors. In breast cancer, stromal inflammatory cells and cancer derived immunoglobulins have been correlated with the progression, malignancy and poor prognosis of the tumor. The results herein reported show that the dog’s mammary gland epithelium also expresses immunoglobulins, and they mostly show a direct relationship with the infiltration of macrophages. In addition, this study shows that the infiltration of mast cells, B-cells and macrophages varies depending on the degree of malignancy of neoplasia.