The FFPE tissue samples were cut into 4 mm thin sections. Slides were incubated for 10 min in 0.3% hydrogen peroxide. Subsequently, sections were incubated overnight at 4°C with the primary antibody. Then, slides were incubated with a secondary antibody [either EnVision + System-HRP Labeled Polymer anti-rabbit or anti-mouse (Dako, Agilent, Santa Clara, United States)]. The average density (cells/mm2) of each lymphocyte subset was calculated from five 1 mm2 regions within each tumor to calculate its average density of positive cells (Reuben et al., 2017 (link)). IPMN was confirmed in all tissue samples by H&E staining, and the grade of dysplasia was evaluated by two experienced pathologists (ZJY and HX).
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