Fig. 2

Definitions of non-cancerous epithelium (NCE) and “distance from the surface of the NCE to the cancer”. In case the atypia of the superficial epithelium was weaker compared with the atypia of the deeper cancer, we judged the epithelium as NCE (Fig. 2a, b green line). We measured the shortest distance from the surface of the NCE to the cancer, which existed just below the NCE in the mucosa, and defined it as the “distance from the surface of the NCE to the cancer” (Fig. 2a, b red arrow). We calculated the percentage of the differentiated-type cancerous portion covered by NCE in each patient. The NCE percentage was calculated as the length of the differentiated-type cancerous portion covered by NCE in all slides divided by the length of the differentiated-type cancerous portion in all slides (Fig. 2c)