EGFR gene mutations in patients with adenosquamous lung carcinoma

Adenosquamous (ADSQ) carcinoma accounts for 1-4% of non-small cell lung cancer (NSCLC). The origin of ADSQ carcinoma and its genetic background is not fully understood. Most studies concerning epidermal growth factor receptor (EGFR) mutation status are performed in adenocarcinoma, while there is limited information about the prevalence of this mutation in ADSQ-bearing Caucasian patients and the efficacy of EGFR tyrosine kinase inhibitors.

EGFR gene status has been examined in 1000 non-squamous NSCLC patients of Polish origin. Polymerase chain reaction (PCR) followed by DNA fragment length analysis and allele-specific PCR as well as real-time PCR technique were used to estimate EGFR gene status. Complete clinical data were obtained for all examined patients.

In the group of 1000 non-squamous NSCLC patients, ADSQ was diagnosed in 14 (1.4%) cases. Activating mutations of EGFR were observed in 28.6% (four out of 14) of ADSQ-bearing patients and included deletions of 15 base-pairs in exon 19 in three cases (one man and two women) and substitution of L861Q with coexistence of G719X mutation in one non-smoking male patient. Deletions were diagnosed in two non-smoking patients and one current-smoking female patient (50 pack-years). One non-smoking man with deletion in exon 19 of EGFR gene was successfully treated with gefitinib in first-line therapy.

EGFR gene mutations in ADSQ carcinoma patients may be more common than previously thought. EGFR mutation testing is appropriate in ADSQ-bearing patients, in which response for molecular-based therapy is predictable.