Histopathological transformation to small-cell lung carcinoma in non-small-cell lung carcinoma tumors

Lung cancer represents the primary cause of cancer mortality worldwide (1). The World Health Organization (WHO) classifies lung cancer into two subtypes: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) (2). NSCLC represents 85% of cases of lung cancer, and is divided into adenocarcinoma, squamous-cell, and large-cell carcinoma (3). SCLC represents 14–15% of all lung cancers, and more than 30,000 new cases are diagnosed each year in the United States (4).The oncogenes involved in lung cancer development have been studied extensively and a great variety of tumor promoter and suppressor genes play important roles in the development of lung cancer (5)