If there are differences in the D2-40 reaction to oral cancer, which has a well-known reactivity to PDPN of both cancer cells and normal cells, and LpMab-23 with a reactivity that is specific to the oral cancer-type PDPN, it may be thought that PDPN conformation is different for different cancers, resulting in the differences in clinical significance for the PDPN expression. This evidence concerns the gene PDPN and lip and oral cavity carcinoma.