Histologic evaluation of host immune microenvironment and its prognostic significance in oral tongue squamous cell carcinoma: a comparative study on lymphocytic host response (LHR) and tumor infiltrating lymphocytes (TILs).

Background: Host immune microenvironment is a key component of anti-tumoral immune response, influencing tumor progression, regression, and treatment responses. There is a need for simple and reliable histologic measurements of host immune response in routine histopathologic diagnosis.
Methods: The prognostic value of lymphocytic host response (LHR), a qualitative histologic grading scheme, was compared to stromal/intratumoral TIL (sTIL/iTIL) percentage, a quantitative measurement in a retrospective study of 329 patients with oral tongue squamous cell carcinoma (OTSCC) of 4 cm or less in size.
Results: High sTIL predicted improved distant recurrence free survival on univariate survival analysis and was an independent prognostic factor for better overall survival on multivariate analysis. LHR and iTIL were not associated with the risk of nodal metastasis or outcome.
Conclusions: sTIL appears to be a superior quantitative histologic measurement for the host immune microenvironment compared with the qualitative LHR grading scheme. sTIL is an independent prognostic factor for overall survival in OTSCC.
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