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Simple Summary: Quantification of tumor infiltrating lymphocytes (TILs) in the cancer microenvironment has become of increasing interest in immuno-oncology and has been therefore studied extensively in all "high prevalence" cancer entities. However, only little is known about TILs infiltration in rare cancer entities, such as vulvar cancer. Here, we have studied an exceptional large multicenter cohort of 530 vulvar squamous cell cancer specimens using immunohistochemistry. The study was conducted using large tissue section to quantitate the CD3+/CD8+ T-cell density along the invasive margin compared to the center of the tumor. The CD3+ T-cell density at the invasive margin showed the strongest prognostic value. Moreover, analysing the interplay between both T-cell densities—at different locations—enabled us to identify three major immune phenotypes that showed strong prognostic relevance. Accordingly, the sole analysis of CD3+ T-cells at the invasive margin—rather than a cumbersome immune score—predicts patient's outcome in vulvar cancer. Background: Although quantification of tumor infiltrating lymphocytes (TILs) has become of increasing interest in immuno-oncology, only little is known about TILs infiltration in the tumor microenvironment and its predictive value in vulvar cancer. Methods: Immunohistochemistry and automated digital image analysis was applied to measure the densities of CD3+ (DAKO, #IR503) and CD8+ (DAKO, #IR623) TILs at the invasive margin and in the center of 530 vulvar squamous cell cancers. Results: An elevated density of CD3+ T-cell at the invasive margin was significantly associated with low tumor stage (p = 0.0012) and prolonged survival (overall survival [OS] p = 0.0027, progression free survival [PFS] p = 0.024) and was independent from tumor stage, nodal stage, grade, and HPV-status in multivariate analysis (p < 0.05). The prognostic impact of CD3+ cells in the center of the tumor was weaker compared to the invasive margin (OS p = 0.046, PFS p = 0.031) and lacking for CD8+ T-cell densities at any location (p ≥ 0.14 each). Unsupervised clustering of CD3+ and CD8+ T-cell densities identified three major subgroups corresponding to the immune desert (137 patients), immune excluded (220 patients) and immune inflamed phenotypes (133 patients). Survival analysis revealed a particular poor prognosis for the immune desert phenotype for OS (p = 0.0071) and PFS (p = 0.0027). Conclusion: Our data demonstrate a high prognostic value of CD3+ T-cells at the invasive margin and immune phenotypes in vulvar squamous cell cancer. [ABSTRACT FROM AUTHOR]