MKI67 and adenocarcinoma: To evaluate whether the established PDXs retained histological characteristics and whether the expression pattern of biomarkers was consistent with the tumor of origin, histopathological and immunohistochemical examinations were performed by staining with H&E and clinically relevant biomarkers, including the primary markers for adenocarcinoma (TTF1), squamous (P40) (Figure 3A), vimentin, Ki67, and EGFR and PD-L1 (Figure 3B).