Morphological tumor-infiltrating lymphocytes evaluation in biopsies from patients with non-small cell lung carcinoma: useful or useless?

<bold>Background:</bold> High levels of tumor infiltrating lymphocytes (TILs) correlates with favorable outcomes in patients with non-small cell lung carcinoma (NSCLC). While immunohistochemistry (IHC) is the standard method for assessing TILs density, using hematoxylin and eosin (H&E) slides for TILs quantification offers a promising alternative, especially in biopsies with limited tumor material. This study aimed to investigate the prognostic significance of TILs in NSCLC using morphological methods on H&E slides. <bold>Methods:</bold> We have retrospectively collected 33 cases of NSCLC between December 2018 and December 2022. TILs were evaluated on H&E slides from biopsy specimens by two pathologists following the International Immuno-Oncology Biomarkers Working Group guidelines. Mononuclear immune cell percentages were quantified, and H&E TILs status was categorized as high or low using a cut-off at the median percentage of TILs. <bold>Results:</bold> The mean age was 56.36 years and male to female ratio of 15.5. Histological subtypes included adenocarcinoma (ADC) (70%), squamous cell carcinoma (SCC) (18%), sarcomatoid carcinoma (6%), and carcinoma NOS (6%). TILs varied from 0 to 80% (mean 30%, median 40%). High TILs scores (≥40%) were found in 45% of cases, with 80% ADC and 13% SCC (p=0.68). No correlation was found between TILs and age, gender, lymph node invasion, metastasis and survival. <bold>Conclusion:</bold> TILs quantification on H&E slides could be indicative of the immune microenvironment, yet limited sample size warrants further studies and correlation with IHC methods.