The first case of lung carcinosarcoma harboring in-frame deletions at exon19 in the EGFR gene.

Mutations of the epidermal growth factor receptor (EGFR) gene play a critical role in carcinogenesis of lung cancer, particularly adenocarcinoma. However, to the best of our knowledge, no mutations of the EGFR in patients with lung carcinosarcoma have been identified. We herein report the case of a 61-year-old female referred for a detailed examination of a left pulmonary mass shadow. Although bronchoscopy was performed, it failed to lead to a diagnosis, and video-assisted thoracoscopic surgery was therefore carried out to diagnose the tumor. The pathology revealed biphasic features consisting of both adenocarcinoma and chondrosarcoma. Intriguingly, both the adenocarcinoma and chondrosarcoma components were proven to harbor an exon19 deletion in the EGFR gene. Although carcinosarcoma is a rare malignancy of the lungs, genetic analyses of oncogenic drivers, such as the EGFR gene, should be conducted.