Structural and Functional Characteristics of Leptomeningeal Lymphatic Vessels in Leptomeningeal Metastases from Lung Cancer Patients

Background: The purpose of this study is to explore whether there are lymphatic vessels in the human leptomeninges, and their potential role in the immune response to central nervous system tumors, in order to determine their significance in the field of tumor biology, especially the role they play in the growth, metastasis, and immune response of tumors. Methods: We used immunohistochemistry and immunofluorescence techniques to examine the leptomeninges in 46 patients diagnosed with leptomeningeal metastasis in cerebrospinal fluid cytology (29 positive biopsy specimens, 17 negative) as well as 11 epilepsy patients. We visualized lymphatic vessels in the human leptomeninges using LYVE1 and PDPN antibodies, labeled tumor cells with CK, T cells with CD3, and blood vessels with CD31 and α-smooth muscle actin. By comparing the lymphatic vessel density and T cell count in tumor areas versus non-tumor areas, and observing whether there was infiltration of tumor cells into the lymphatic vessels, we analyzed the presence and function of human leptomeningeal lymphatic vessels. Results: The research results confirmed the existence of lymphatic vessels in the human leptomeninges, with a significant increase in lymphatic vessel density and T cell count around the tumor compared to non-tumor areas (P < 0.05). At the same time, infiltration of tumor cells was observed within the lymphatic vessels. Conclusions: These findings suggest that the lymphatic vessels in the leptomeninges not only structurally resemble extracranial brain lymphatic vessels, but also function similarly in tumor immune response and metastasis pathways. These findings challenge traditional understanding of immune responses to central nervous system tumors and provide important clues for further research on the role of intracranial lymphatic vessels in tumor biology.