LAUSR

OBJECTIVES The prognostic significance of blood and lymphatic vessel invasion in the 8th edition of the Tumor, Node, Metastasis (TNM) classification remains unclear. Therefore, this study aimed to evaluate the prognostic significance of blood and lymphatic vessel invasion in p-stage IA lung adenocarcinoma in the 8th edition of the TNM classification. MATERIALS ANDMETHODS We retrospectively examined patients with p-Stage 0-IA lung adenocarcinoma, reclassified according to the 8th edition of the TNM classification. Blood and lymphatic vessel invasion were evaluated using hematoxylin-eosin and Elastica van Gieson and hematoxylin-eosin and anti-podoplanin antibody staining, respectively. Combined blood and lymphatic vessel invasion constituted tumor vessel invasion (TVI). RESULTS Overall, 306 patients were evaluated. The median follow-up period was 98.0 (range: 10-216) months. The 5-year recurrence-free survival differed significantly among patients with and without TVI in p-stage IA1 (TVI-: 100%, TVI+: 88.9%, P = 0.007) and IA2 (TVI-: 94.6%, TVI+: 80.8%, P = 0.012) but not in p-stage IA3 (TVI-: 66.7%, TVI+: 75.0%, P = 0.598). The 5-year lung cancer-specific survival also differed significantly among those with and without TVI in p-stage IA1 (TVI-: 100%, TVI+: 88.9%, P < 0.001) and IA2 (TVI-: 98.2%, TVI+: 88.7%, P = 0.043) but not in p-Stage IA3 (TVI-: 66.7%, TVI+: 75.0%, P = 0.858). No recurrence and lung cancer-specific deaths occurred in p-stage IA1 patients without TVI. On multivariate analysis, the presence of TVI was independently associated with recurrence and lung cancer-specific death in patients with p-stage IA1-2 lung adenocarcinoma. TVI did not affect the prognosis of those with p-stage IA3 adenocarcinoma. CONCLUSION TVI is a prognostic factor in patients with p-stage IA1-2 lung adenocarcinoma. P-stage IA1 lung adenocarcinoma without TVI may therefore be classified as minimally invasive.