PIK3CA and gastric cancer: PIK3CA mutation revealed high intratumoral heterogeneity characterized with three to five different PIK3CA genotypes (including wildtype) in EBV-positive gastric cancer.57 Additionally, analyzing mutation signatures in the Catalog Of Somatic Mutations In Cancer34 indicated an intimate correlation between the TMEscore and mismatch repair associated signature 6 (online supplemental figure S9C and online supplemental table S12).