Also, a patient with squamous cell carcinoma of head and neck with wt PIK3CA and an EGFR exon 21 mutation (H835L) in an initial resected tumor was found to have a PIK3CA E545K mutation (0.05%) in cfDNA collected after progressive disease following 3 months of cetuximab, carboplatin and paclitaxel treatment. Here, EGFR is linked to squamous cell carcinoma.