['A radical resection is considered to be the most effective treatment for resectable non-small cell lung cancer. However, even when resected in early stages (T1aN0, T1bN0) up to 20% of patients will experience recurrence. The aim of this retrospective study was to evaluate the prognostic influence of lymphatic vessel invasion (LVI) in stage IA adenocarcinoma patients.', 'From January 1983 to June 2003, a total of 229 consecutive patients with pT1a or T1b N0 M0 lung adenocarcinoma who had undergone radical resection and lymph node dissection were retrospectively reviewed. Sections stained by the hematoxylin-eosin and the Elastica van Gieson method were examined for the presence of LVI. The overall survival was estimated using the Kaplan-Meier method, log-rank test, and the Cox proportional hazards analysis.', 'The median follow-up was 81 months. A total of 143 patients (62%) were able to be diagnosed with regard to the presence of LVI, while information was not provided for 86 patients (38%), who were therefore excluded from the study. LVI was noted in 22 of the evaluable patients (15%) and was not seen in the other 121 patients (85%). The 5-year overall survival rate of the LVI-negative group and the LVI-positive group was 94.5 and 70.9%, respectively (P = .003). A multivariate analysis revealed LVI to be an independent predictive factor (hazard ratio: 0.202; P = .001).'] Is lymphatic vessel invasion a significant prognostic indicator in stage IA lung adenocarcinoma?