Epidermal Growth Factor Receptor (EGFR) overexpression can occur in a variety of tumor types, including breast, prostate, ovarian, brain, lung and predominantly squamous cell carcinomas. Tumors that express EGFR are associated with a poor prognosis and a shorter disease-free survival. Most colon carcinomas will show expression of EGFR in more than 1% of the invasive tumor cells. Patients whose tumor expresses EGFR and are wild-type for KRAS mutation are eligible for cetuximab therapy based on the status of RAS mutation.
EGFR immunohistochemistry (clone D38B1; non-mutation specific) has no relationship to determining clinical response to EGFR–tyrosine kinase inhibitors in lung adenocarcinoma. The appropriate study to evaluate somatic mutations in the tyrosine kinase domain of EGFR gene in lung adenocarcinomas is EGFR Mutation Analysis by either PCR or NGS methods.