INTRODUCTION
Mucosal melanoma is a tumor type with a low incidence rate but it is highly malignant. Although it is one of the most common subtypes of melanoma in China [1], only a limited number of cases have been reported with no support from large datasets. The related literature is mostly on clinical analysis of head and neck mucosal melanoma [2], and this has an impact on our understanding and clinical treatment of this disease. With the development of immunotherapy, researchers are increasingly studying the immune microenvironment of this tumor type. Current research is focused on providing theoretical support and laboratory research on the clinical application of immunotherapy in this setting. Unlike other types of melanoma, mucosal melanoma does not benefit significantly from immunotherapy as it has the characteristics of low tumor mutation load and low lymphocyte infiltration. T cells are important functional cells in tumor immunity and play an important role in tumor-related immune processes. CD3 is a specific marker on the surface of T cells, and CD3 immunohistochemical staining can effectively evaluate the infiltration level of T cells in tumor tissue [3]. CD8 + T cells are the main lymphocyte subsets infiltrating the tumor microenvironment [4]. Previous studies have also confirmed that CD4 + and CD8 + T lymphocyte infiltration can reflect anti-tumor immune function to a certain extent [5].
Through analysis of the pathological results from patients with a previous diagnosis of mucosal melanoma and subsequent treatment, we aimed to explore the local infiltration of CD3, CD4, and CD8 lymphocytes in this tumor type. We also examined the relationship of these lymphocytes to the general characteristics of the disease and the expression of PD-1 and PD-L1 in the tumor. From this, we hope to further our understanding of the characteristics of mucinous melanoma in head and neck, and thus aid clinical practice.