Prognostic impact of micropapillary and solid histological subtype on patients undergoing curative resection for stage I lung adenocarcinoma according to the extent of pulmonary resection and lymph node assessment

Background: We aimed to evaluate the impact of micropapillary and/or solid (MPSOL) components on survival and recurrence of patients with resected stage I lung adenocarcinoma (LUAD) according to the extent of surgery and completeness of lymph node assessment (LNA). Methods: We retrospectively reviewed 1886 consecutive patients who underwent surgical resection for pathologic stage I LUAD between 2009 and 2014. The patients were classified by the presence (≥1%) of MPSOL into the MPSOL(+) (n = 489) and MPSOL(−) (n = 1397) group.We analyzed the outcomes according to the extent of surgery (sublobar resection [SR] vs. lobectomy) and the LNA (complete vs. incomplete). Complete LNA was defined as systematic LN dissection according to European Society of Thoracic Surgeons guideline. Results: In the MPSOL(+) patients, there was no significant difference in adjusted overall survival (OS), recurrence-free survival (RFS), and recurrence pattern between the lobectomy and SR group. Of note, patients with complete LNA had higher adjusted OS and RFS than those with incomplete LNA (aOS, 86.3% vs. 78%, p = 0.002; aRFS, 70% vs 63.1%, p = 0.06). In the MPSOL(−) patients, adjusted RFS of the SR group was better than the lobectomy group (95% vs. 90.5%, p = 0.021), although there was no difference in survival regarding to the LNA. Complete LNA was a favorable prognostic factor for RFS in the MPSOL(+) patients (HR = 0.463, 95% CI: 0.227–0.944, p = 0.034). Conclusions: In MPSOL(+) patients, complete LN assessment affects the OS and RFS rather than the extent of lung resection. In patients with solid tumor or tumor>2 cm, a complete LN assessment would be required, even if sublobar resection is unavoidable.