Intra-Tumour Heterogeneity Is One of the Main Sources of Inter-Observer Variation in Scoring Stromal Tumour Infiltrating Lymphocytes in Triple Negative Breast Cancer

Stromal tumour infiltrating lymphocytes (sTILs) are a strong prognostic marker in triple negative breast cancer (TNBC). Consistency scoring sTILs is good and was excellent when an internet-based aid developed by the TIL-WG used to score cases reproducibility study. This study aimed evaluate of assessment using this from routine practice explore potential tool overcome variability scoring. Twenty-three pathologists scored digitized slides 49 TNBC biopsies aid. Subsequently, fields view (FOV) each case were selected one pathologist group tool. Inter-observer agreement for absolute (ICC 0.634, 95% CI 0.539–0.735, p < 0.001) but poor fair binary cutpoints. heterogeneity main contributor disagreement. When same FOV case, inter-observer 0.798, 0.727–0.864, 20% 0.657, 0.561–0.756, 40% 0.644, 0.546–0.745, However, there wide range scores many cases. Reproducibility used. Heterogeneity variance will need be analytic validity achieved.