Our study included 609 patients with clinical T1 N0 M0 lung adenocarcinoma; 568 (93.3%) pathologic node negative [pN(–)] and 41 (6.7%) pathologic node positive [pN(+)] patients, diagnosed after complete surgical resection. The association between prognosis and pathologic findings was analyzed retrospectively.
pN(+) patients had a significantly lower lepidic growth component ratio (10% vs 50%), a higher lymphatic invasion (LI) rate (68% vs 11%), vessel invasion rate (59% vs 14%), and visceral pleural invasion rate (29% vs 9%), compared with pN(–) patients (all Ps < .001). Surprisingly, 13 of 41 (32%) pN(+) patients showed no LI. In pN(–) patients, a multivariate analysis of recurrence-free survival revealed that lower lepidic growth component ratio, and lymphatic, vessel, and pleural invasion were significantly correlated with a poor prognosis (P = .008, .045, .031, and .024). However, in pN(+) patients, the multivariate analysis of recurrence-free survival showed that only LI was a significant independent prognostic factor (P = .037). The 5-year recurrence-free survival rates were as follows: 91.2% for pN(–)/LI(–) patients, 68.2% for pN(–)/LI(+) patients, 63.5% for pN(+)/LI(–) patients, and 41.9% for pN(+)/LI(+) patients. LI status stratified the prognosis not only in patients with no nodal metastasis but also in those with metastasis.
LI, which is not always present in node-positive adenocarcinoma, is an important prognostic variable in patients with node involvement.