Qualitative Morphological Assessement of Tumor Associated Lymphatic Vasculature in Mammary Gland Neoplasia of Female Dog in Relation with Sentinel Lymph Nodes Metastatic Infiltration

Metastasis, the spread of tumor cells from the primary site to lymph nodes and the distant organs is the most aggressive and specific feature of malignant cancer. The mechanisms by which malignant cells leave the primary tumor, invade lymphatics and metastasize are complex and interconnected being directly related to biological behavior of tumor. However, the lymphatic vasculature is often neglected. The aim of this study is to establish if there is a correlation between the peritumoral and intratumoral lymphatic vascular density and the presence of metastatic infiltration in sentinel lymph nodes of mammary gland tumor. Injecting the coloring solution in mammary gland tumor of nine female dogs it was noted the pattern of lymphatic vessels at the injection site, their density, size distribution area, their trajectory to the first lymph node. Also the status of the tumor draining lymph node was histological assessed. The architecture and density of intratumoral and peritumoral lymphatic vessels was determined by their function in absorbing interstitial fluid together with the tumoral cells, due to their permeability. The coloring solution show the sinuous pattern of peritumoral lymphatic vessels, with a rich chaotic vascular network compared with reticular or plexiform pattern of lymphatic vasculature of healthy mammary gland. The size of peritumoral lymphatic colored area was dependant on the histological type of the tumor and on its size. Also, a malignant tumor size >1cm was associated with the presence of the metastatic infiltration in the first tumor draining lymph node. The density of intratumoral lymphatic vessels was low compared with the peritumoral lymphatics. In conclusion, qualitative morphological assessment of lymphatic vasculature of malignant mammary gland tumors of female dog revealed an increased density of lymphatic vessels in the peritumoral region and a lesser degree intratumoraly. The size of peritumoral lymphatic area was directly related with the presence of metastases in sentinel lymph nodes. Although great progression has been made in revealing the lymphangiogenic markers, additional studies are required to understand the paradoxical significance of intratumoral and peritumoral lymphatics density and lymph nodes metastases for prognosis and development of metastases in vital organs.