215 Reproducibility study on invasiveness of pulmonary AdC with a modified classification To examine the location of the invasive areas assigned by all pathologists within each case we developed a method of heatmap analysis. A visual summary with a color scheme shows areas with low and high agreement for invasiveness. Heatmaps were generated for all cases, and examples of unanimous invasive cases and on the cases with discordance in invasion assessment, are shown in Figure 4. A round shape of the hotspot (red) area denotes agreement among numerous pathologists. Figure 4. Examples of heatmap overlays are shown for 6 cases in 1st and 2nd round. Note the similarities between the 1st and 2nd rounds. A: Tumor with large invasive area and high concordance. B: Tumor with focal area of invasion; C: Relatively low number of invasive scores with smaller focus of possible invasion in the 2nd round; D: relative increase in areas of possible invasion without a focus; E: separation and reduction of possible invasion focus; F: Sharp focus of two rounds of possible invasive areas in the 2nd round. Of note, a round hotspot area (red) denotes invasion by more than a few pathologists, while dispersed, angulated red areas point to variation in location and length of invasive size. The heatmap does not provide information about the pathologists scoring a case as non-invasive. The highest agreement occurred in cases with clear invasion in practically the whole tumor, resulting in low measurement variation (Figure 5). 15
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