PIK3CA and esophageal squamous cell carcinoma: The first report that PIK3CA mutation was closely related to a longer prognosis in ESCC was provided by Shigaki H et al. [55], who, using 219 Japanese ESCC samples by means of pyrosequencing, showed that Japanese patients with PIK3CA mutations in exons 9 and/or 20, regardless of whether single or multiple mutations occurred concomitantly, had significantly better disease-free survival and overall survival.