10.1371/journal.pone.0190158 James Ziai James Ziai Houston N. Gilbert Houston N. Gilbert Oded Foreman Oded Foreman Jeffrey Eastham-Anderson Jeffrey Eastham-Anderson Felix Chu Felix Chu Mahrukh Huseni Mahrukh Huseni Jeong M. Kim Jeong M. Kim CD8+ T cell infiltration in breast and colon cancer: A histologic and statistical analysis Public Library of Science 2018 FFPE TIL results show CD 8 immunohistochemistry cytotoxic T cell infiltration cytotoxic T cell prevalence tissue sample marker variability histologic sections ROI CD 45RO findings support cytotoxic tumor biopsy fragments CD 3 UICC colorectal cancer samples tissue samples chromogenic immunohistochemistry marker prevalence biomarker strategies breast carcinomas tumor types T cell biomarker assessment CD 8 counts prognostic value breast cancer patients patient sample colon cancer patients tumor section step sections colon cancer Statistical analyses 2018-01-10 18:33:39 Dataset https://plos.figshare.com/articles/dataset/CD8_T_cell_infiltration_in_breast_and_colon_cancer_A_histologic_and_statistical_analysis/5775315 <div><p>The prevalence of cytotoxic tumor infiltrating lymphocytes (TILs) has demonstrated prognostic value in multiple tumor types. In particular, CD8 counts (in combination with CD3 and CD45RO) have been shown to be superior to traditional UICC staging in colon cancer patients and higher total CD8 counts have been associated with better survival in breast cancer patients. However, immune infiltrate heterogeneity can lead to potentially significant misrepresentations of marker prevalence in routine histologic sections. We examined step sections of breast and colorectal cancer samples for CD8+ T cell prevalence by standard chromogenic immunohistochemistry to determine marker variability and inform practice of T cell biomarker assessment in formalin-fixed, paraffin-embedded (FFPE) tissue samples. Stained sections were digitally imaged and CD8+ lymphocytes within defined regions of interest (ROI) including the tumor and surrounding stroma were enumerated. Statistical analyses of CD8+ cell count variability using a linear model/ANOVA framework between patients as well as between levels within a patient sample were performed. Our results show that CD8+ T-cell distribution is highly homogeneous within a standard tissue sample in both colorectal and breast carcinomas. As such, cytotoxic T cell prevalence by immunohistochemistry on a single level or even from a subsample of biopsy fragments taken from that level can be considered representative of cytotoxic T cell infiltration for the entire tumor section within the block. These findings support the technical validity of biomarker strategies relying on CD8 immunohistochemistry.</p></div>