Does TLS Exist in Canine Mammary Gland Tumours? Preliminary Results in Simple Carcinomas

Abstract

Neoplastic progression is influenced by the expression of tumour antigens that activate an anti-tumour immune response. Human medical studies show that this body defence is carried out in secondary lymphoid organs (SLOs) but also directly in the tumour through organized cellular aggregates that are called tertiary lymphoid structures (TLSs). However, their occurrence has different meanings in different tumour types. For example, the presence of TLSs in breast cancer is associated with the most aggressive subtypes. This paper aimed to study TLSs in canine mammary simple carcinomas. A morphological assessment of the inflammatory infiltrate was performed on H&E sections of fifty cases. Immunohistochemistry was then carried out to typify the inflammatory cells in the tumour microenvironment. Results showed that, sometimes, inflammatory infiltrates were organized in follicles close to high-grade carcinomas, simulating a lymphoid organization, as in breast cancer. Therefore, we can assume that even in canine mammary tumours, TLSs exist and they are entities to consider due to their presence in the most aggressive histotypes or tumours with a high degree of malignancy.

Hemosiderin-Laden Macrophages in Canine Mammary Carcinomas

“…Nevertheless, the greater positivity was concentrated near TLSs. In a previous study, we found TLSs were often located near or around vessels with emboli, so we hypothesized that they could be involved in the metastatic process, as already reported in human medicine [61,68]. In the same way, HLMs could have a potential metastatic role.…”

“…Inflammatory cells can be organized in conspicuous groups of only lymphocytes (TILs) or in more complex structures of mixed populations, simulating lymphoid tissues (TLSs). In canine mammary tumors, as in breast cancer, TLSs can be described with different patterns of organization and are characterized by the presence of HEVs [61]. In this study, conspicuous groups of HLMs were located in the marginal areas of TILs or TLSs and were positive for VEGF, suggesting that they also have an angiogenic role in the development of HEVs.…”