In addition, serum tumor markers including carcinoembryonic antigen (CEA), cyfra21-1 (cytokeratin 19 fragment), squamous cell carcinoma (SCC), and CA72-4 (tumor-associated glycoprotein 72) were tested in 12 of the patients preoperatively, yet none presented positive results. This evidence concerns the gene KRT19 and squamous cell carcinoma.