Further, a patient with mucoepidermoid carcinoma of the nasal-lacrimal sac with wt PIK3CA and an EGFR exon 18 mutation (A722V) on an initial biopsy was also found to have a PIK3CA E545K mutation in cfDNA, and the patient was ultimately refractory to treatment with the EGFR tyrosine kinase inhibitor erlotinib. The gene discussed is PIK3CA; the disease is mucoepidermoid carcinoma.