ABO and esophageal squamous cell carcinoma: The ABO blood group has been demonstrated to be associated with clinical outcomes of pancreatic cancer (Rahbari et al., 2012), esophageal squamous cell cancer (Sun et al., 2014), colon cancer (Cao et al., 2014), nasopharyngeal cancer (Ouyang et al., 2013), and breast cancer (Cihan, 2014).