Abstract: Objective To identify independent predictors of prognosis in MMNS and to examine the expression of CD4, CD8, CD20 and their relationship with prognosis. Methods 87 patients with MMNS were retrospectively analyzed to summarize their clinicopathologic characteristics; the expression of CD4, CD8, and CD20 in MMNS were observed by EnVision immunohistochemical staining (IHC) to analyze the relationship between the expression of these markers and prognosis. Results MMNS with sinus, surrounding tissue invasion, larger tumor and higher AJCC stage showed a worse prognosis. No significant correlation was found among sex, age, histological type,melanin granules, mitotic figures and survival rate. The counts of CD4⁺, CD8⁺ and CD20⁺ TILs in intra-tumoral stroma were positively correlated with the density of TILs at the base of the tumor. CD20⁺ B cells did not have a central tendency to aggregate to form tertiary lymphoid structures, whether in the intratumoral stroma or in the basal stroma of the tumor, the three cell subsets were admixed. There was no statistically significant difference in OS between CD4⁺, CD8⁺, and CD20⁺ subsets. Conclusions The number of CD20⁺ B cells was significantly less than that of CD4⁺ and CD8⁺ T cells in both the intratumoral stroma and the basal stroma of the tumor, and tertiary lymphoid structures fail to be formed, which, unlike cutaneous malignant melanoma, might be a cause of the poor prognosis of MMNS.

Key words: malignant melanoma in nasal cavity and paranasal sinuses, tumor infiltrating lymphocytes, CD4, CD8, CD20