Stroma-tumour fraction was determined on H&E stained histological sections. H&E stained sections were routinely estimated under 10 × 10 lens microscope to select the sections rich in tumour (tumour tissue > 50%, necrotic tissue < 10%). The stroma-tumour fraction was measured by Stroma Analyzer (Room 4, Kent, UK), as was described by Danielsen et al. 29 (link) Briefly, the whole slides images of H&E stained sections were scanned with an Aperio AT2 digital slide scanner at ×40 (Leica, Germany), giving a resolution of 0.23 µm per pixel. Images with a resolution of 1.82 µm per pixel were used for image processing. A senior pathologist (Li Zhang) marked the tumour areas on the scanned images by using the software tool (Stroma analyzer, Room 4, Kent, UK). The stroma fraction in the selected tumour region was automatically calculated by the software (Stroma analyzer, Room 4, Kent, UK). Tumours with stroma fraction less than or equal to 0.50 were labelled low stroma, while those with stroma fraction greater than 0.50 were labelled high stroma.
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