EGFRpositive

EGFR-positive refers to cells or tumors that express or carry activating changes in the epidermal growth factor receptor (EGFR), a transmembrane receptor tyrosine kinase that transduces signals for cell proliferation, survival, and differentiation. In oncology, EGFR status may be described as positive due to overexpression of the protein, gene amplification, or activating mutations in the EGFR gene. The significance of EGFR positivity depends on the mechanism detected; overexpression alone does not reliably predict response to targeted therapy, whereas activating mutations often do.

Testing for EGFR status uses immunohistochemistry to assess protein expression, fluorescence in situ hybridization or copy-number analysis for amplification, and DNA sequencing or targeted panels for mutations in exons 18–21. In contemporary practice, EGFR mutation status is most relevant in non-small cell lung cancer (NSCLC), where common exon 19 deletions and L858R mutations predict sensitivity to EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib, erlotinib, afatinib, and osimertinib. In colorectal cancer, EGFR-targeted antibodies (cetuximab, panitumumab) are effective in tumors that are wild-type for KRAS/NRAS and BRAF, and their benefit is not simply determined by EGFR protein overexpression. Head and neck squamous cell carcinomas may express EGFR, and anti-EGFR therapies can be used in selected cases.

Resistance mechanisms, including the T790M mutation, MET amplification, and histologic changes, limit durability of responses. Accurate, context-specific interpretation of EGFR status—distinguishing expression from mutation and integrating other biomarkers—is essential for guiding therapy and prognosis.