Although the morbidity of multiple primary lung cancer (MPLC) has been increasing year by year, it is still controversial about pathogenesis, differential diagnosis and management strategies of MPLC. hTis review provides a snap-shot of the main progress of pathogenesis, differential diagnosis and management strategies of MPLC.

Background and objective Synchronous multiple primary lung cancer (sMPLC) is a sparse disease in the past, but there has been a gradual increase in the morbidity of sMPLC recently. However, studies on large sample have never been undertaken. hTe purpose of this study is to investigate the diagnosis, treatment and prognosis of sMPLC through analyzing the clinical data, and provide supports for the management of sMPLC. Methods According to Martini-Melamed criteria, 357 patients were diagnosed sMPLC. hTe pathological staging is on the basis of the 8th edition tumor-node-metastasis (TNM) staging from International Association for the Study of Lung Cancer (IASLC). Results There were 269 patients with double primary lung cancer, 65 patients with triple primary lung cancer and 23 patients with four or more primary lung cancer. Lesions (68.55%, 571/833) were frequently in upper lobe, especially the right upper lobe. Adenocarcinoma (95.56%, 796/833) was the mainly pathological type, followed by squamous cell carcinoma (2.40%, 20/833). hTe acinar predominant subtype was the main part (70.81%, 313/442) of the all adenocarcinoma specimens. Most of the lesions (68.35%, 244/357) were stage Ib or low. Among the initial lesion and the following lesions ,patients who had the same pathological type (92.72%, 331/357) were more than the different (7.28%, 26/357), of which adenocarcinoma-adenocarcinoma occupied the major pro-portion (99.40%, 329/331). hTe 3-year overall survival (OS) and 5-year overall survival were respective 91.93%and 84.37%. Multivariate analysis found that smoking history (P=0.012), the diameter of the maximum lesion (P=0.027), lymph node me-tastasis (P=0.015) and pleural invasion (P<0.001) were the independent risk factors for prognosis. Conclusion Tumours in patients with sMPLC are more frequently in the right upper lobe. Adenocarcinoma was the mainly pathological type. Smoking history, the diameter of the maximum lesion, lymph node metastasis and pleural invasion were the independent risk factors for prognosis. Early diagnosis and active operation can obtain better prognosis.