ObjectiveTo evaluate the prognostic significance of visceral pleural invasion in diameter 3-5 cm nonsmall cell lung cancer(NSCLC). MethodsA total of 112 patients who underwent lobectomy and pathologically diagnosed with NSCLC(3-5 cm) were included in our hospital between January 2006 and December 2010.There were 72 males and 40 females at average age of 61(28-72) years. There were 62 patients diagnosed as adenocarcinoma and 44 as squamous cell lung cancer. Viceral pleural invasion(VPI) was identified in 63 patients as a VPI group. The other 49 patients without VPI were as a NVPI group. All patients were performed with lobectomy and mediastinal lymph node dissection. ResultsThere was no perioperative mortality. More smokers were included in the VPI group when compared with the NVPI group(53.9% vs. 28.6%, P=0.007). More squamous cell cancers were included in the VPI group, while more adenocarcinoma were included in the NVPI group with a statistical difference(P=0.003). The average follow-up duration was 52 months. A total of 32 death occurred at the endpoint. The overall survival(OS) of all included patients was 71.4%. The average follow-up duration was 51 months in the VPI group and 54 months in the NVPI group(P=0.441). There was no statistical difference in OS between the VPI group and the NVPI group(61.7% vs. 83.7%, P=0.017). Cox regression showed age less than 65 years(P=0.007), TNM stage(P=0.013), and VPI(P=0.035) were significant prognostic factors for NSCLC. ConclusionWe identified the presence of VPI as an independent poor prognostic factor in NSCLC patients with diameter at 3-5 cm.