Predictive factors for lymph node metastasis in clinical stage IA lung adenocarcinoma

Systematic lymph node dissection or sampling in all patients with clinical stage IA lung adenocarcinoma is currently controversial because the risk of lymph node metastasis is unclear. This study aimed to determine the predictive factors for lymph node metastasis in patients with clinical stage IA lung adenocarcinoma.

The records of 651 consecutive patients with clinical stage IA lung adenocarcinoma who underwent surgical resection were retrospectively reviewed. The tumors were categorized according to preoperative computed tomography findings as nonsolid (pure ground-glass opacity), part solid, or pure solid. Positron emission tomography with evaluation of the maximum standardized uptake value was performed in 219 patients. Clinicopathologic factors predicting hilar and mediastinal lymph node metastasis were identified by univariate and multivariate analyses.

Tumors were classified as nonsolid in 55 patients (8.4%), part solid in 292 (44.9%), and pure solid in 304 (46.7%). Sixty-nine patients (10.6%) had lymph node metastasis, including 43 (6.6%) with pN1 and 26 (4.0%) with pN2. Ground-glass opacity status (part solid or pure solid), serum carcinoembryonic antigen level (>5 ng/dL), histologic subtype (acinar predominant, papillary predominant, micropapillary predominant, or solid predominant), and maximum standardized uptake value (>5) were identified as significant predictors of lymph node metastasis.

Systematic lymph node dissection should be performed in patients with clinical stage IA lung adenocarcinoma with part-solid or pure-solid tumors, especially those with a carcinoembryonic antigen level exceeding 5 ng/dL and a maximum standardized uptake value exceeding 5. The intraoperative diagnosis of histologic subtype may help to identify patients in whom systematic lymph node dissection can be omitted.