ObjectiveTo observe the outcome of left lung cancer underwent surgical treatment and to analysis the relative risk factors for 4L lymphatic metastasis. MethodsWe retrospectively analyzed the clinical data of 643 lung cancer patients who had underwent mediastinal lymph node dissection intraoperatively in our hospital between January 2011 and December 2013. There were 430 males and 213 females with a mean age of 60.2±9.6 years(range 22 to 83 years), 260 patients had their 4L lymph node dissected, while other 383 patients did not. ResultsAmong 260 patients with 4L lymph node dissected, 44(16.9%) were found 4L lymph node metastasis pathologically. And the results indicated that station 5 lymph node metastasis(P=0.000, OR=12.108 with 95%CI 4.564 to 32.122), station 7 lymph node metastasis(P=0.000, OR=8.496 with 95%CI 2.594 to 27.827), station 8 lymph node metastasis(P=0.029, OR=24.915 with 95%CI 1.395 to 444.948), station 10 lymph node metastasis(P=0.014, OR=3.983, 95%CI 1.321 to 12.009) were independently associated with high risk for 4L lymph node metastasis. Conclusion4L lymphadenectomy should be performed for left invasive lung cancer regularly, especially for patients with hilar lymph node and other mediastinal lymph node metastasis.