Identical epidermal growth factor receptor mutations in adenocarcinomatous and squamous cell carcinomatous components of adenosquamous carcinoma of the lung

BACKGROUND. Adenosquamous carcinoma of the lung is composed of adenocarcinomatous and squamous cell carcinomatous components. The epidermal growth factor receptor (EGFR) mutations occur mostly in adenocarcinomas and rarely in squamous cell carcinoma of lung. Attempts to investigate the EGFR mutation status in each component of adenosquamous carcinoma and to characterize the patients according to mutation status may help to understand the histogenesis of adenosquamous carcinoma. METHODS. The mutation status of EGFR kinase domain from exon 18 to 21 was investigated in 25 Korean patients with adenosquamous carcinoma by polymerase chain reaction-single strand conformation polymorphism using the tissues of each component from the adenosquamous carcinoma tumor. Clinicopathologic characteristics of the patients according to the status of EGFR mutations were compared. RESULTS. EGFR mutations were identified in 11 (44%) patients: 9 mutations were in exon 19, 1 in exon 20, and I in exon 21. EGFR mutations were significantly more frequent (P = .005) in women (n = 8, 80%) than men (n = 3, 20%). Never-smokers (n = 8, 62%) had EGFR mutations more commonly than smokers (n = 3, 25%; P = .111). Identical EGFR mutations in both components of adenosquamous carcinoma were confirmed by nucleotide sequencing. CONCLUSIONS. The frequency of EGFR mutation and clinicopathologic characteristics of the EGFR mutants in adenosquamous carcinoma are similar to those of Asian patients with adenocarcinomas. Identical EGFR mutations in both components suggest the possibility of monoclonality in the histogenesis of adenosquamous carcinoma.