Copy number gain of the PIK3CA region has been documented to be important in HNSCC, but the reported finding [21] is somewhat contradictory to our results because it conferred poor survival to metastatic HNSCCs with unaffected lymph nodes, whereas our study showed more PIK3CA copy number gains in cancers with affected lymph nodes (Table 3). This evidence concerns the gene PIK3CA and head and neck squamous cell carcinoma.