PIK3CA and head and neck squamous cell carcinoma: In one study, the saliva from 93 head and neck squamous cell carcinoma (HNSCC) patients were analyzed for human papilloma virus (HPV) DNA (HPV16/18) and/or somatic mutations (TP53, PIK3CA, CDKN2A, FBXW7, HRAS, and NRAS) related to HNSCC using a multiplex panel of PCR primers [109].