EGFR mutation exists in squamous cell lung carcinoma.

Area of Science:

• Oncology
• Pulmonology
• Molecular Biology

Background:

• The presence of EGFR mutations in lung squamous cell carcinoma (SCC) is debated.
• Adenosquamous carcinoma, often mistaken for SCC, frequently has EGFR mutations.
• Positive responses to tyrosine kinase inhibitors (TKIs) in SCC lack clear correlation with EGFR mutation status.

Purpose of the Study:

• To investigate the occurrence of EGFR mutations in a cohort of lung SCC.
• To accurately confirm squamous differentiation using a panel of markers.
• To assess the clinical response to TKIs in EGFR-mutated SCC cases.

Main Methods:

• Reviewed 191 lung SCC cases diagnosed between 2000-2011.
• Utilized immunohistochemistry (p40, p63, CK5/6, TTF-1) and mucicarmine staining on tissue microarrays.
• Evaluated EGFR mutation status and correlated findings with morphological and immunohistochemical profiles.

Main Results:

• Four cases (approximately 2.1%) were found to have EGFR mutations.
• Three EGFR-mutated cases exhibited definitive SCC features.
• One case was reclassified as adenosquamous carcinoma.
• Two patients with EGFR-mutated SCC showed mixed responses to TKI therapy.

Conclusions:

• A small but distinct subset of rigorously confirmed lung SCC harbors EGFR mutations.
• EGFR-mutated lung SCC may exhibit limited or mixed responses to tyrosine kinase inhibitors.
• Accurate pathological diagnosis is crucial for understanding EGFR mutation relevance in lung carcinomas.