PDPN and undifferentiated carcinoma: Regarding undifferentiated carcinomas, we propose that these tumors can be subclassified based on the immunohistochemical profile into three groups: possible adenocarcinoma (2/14 cases; 14.3%) characterized by positivity for HNF-1β and negativity of p40 and D2-40; possible SCC (5/14 cases; 35.7%) characterized by positivity for p40/p63, variable expression of D2-40 and negativity for HNF-1β; undifferentiated carcinoma, NOS (7/14 cases; 50%) characterized by HNF-1β, p63/p40, and D2-40 negativity.