The Role of Hemosiderin-Laden Macrophages (HLMs) in the Metastasis of Mammary Gland Cancers in Bitches.

Mammary gland tumors are among the most common neoplasms in female dogs. Macrophages are believed to play an important role in tumor progression and metastasis. The aim of this study was to determine whether hemosiderin-laden macrophages (HLMs) may be involved in the development of metastatic lesions in regional lymph nodes. Forty-two cases of mammary gland cancers in female dogs and their regional lymph nodes were included in the analysis. The samples were divided into two groups based on the presence or absence of metastases. The sections were stained with hematoxylin and eosin (HE) and Prussian blue and were additionally subjected to immunohistochemical labeling using antibodies against pan-cytokeratin (Pan-CK) and Ki-67. In 20 cases, no metastatic changes were detected in the regional lymph node, whereas metastases were identified in 22 cases. A positive correlation was observed between the number of HLMs in the tumor stroma and the number of HLMs in the regional lymph node. Furthermore, a positive correlation was found between Ki-67 nuclear immunoreactivity in the mammary tumor and the number of HLMs present within its stroma. HLMs may represent a component of the tumor microenvironment that promotes cancer cell proliferation and potentially contributes to the propensity for metastasis formation in mammary tumors of female dogs.