TTF1 and neoplasm: To evaluate whether stable xenografts retained histological features and if the expression pattern of a number of selected biomarkers was consistent with the tumor of origin, we conducted comparative histopathological and immunohistochemical analyses of outgrowth using clinically relevant biomarkers (e.g., TTF1, p63), and compared the biomarker status with the tumor of origin (Figs.1 and 2).