Lymph node involvement influenced by lung adenocarcinoma subtypes in tumor size ≤3 cm disease: A study of 2268 cases

Aims: Whether lung adenocarcinoma subtype has influence on lymph node involvement in small-sized lung cancer is still unclear. If it has, we want to clarify the extent of the impact. Methods: We identified 2268 operable lung adenocarcinoma patients with tumor size <= 3 cm who had undergone a lobectomy and systematic nodal dissection at Shanghai Chest Hospital between July 2012 and December 2014. The histologic subtypes of all patients were classified according to the IALSC/ATS/ERS classification. The relationship between lymph node involvement and clinicopathologic characteristics was evaluated. Results: Lymph node involvement (pNl+ pN2) was found in 7 of 220 (3.2%) patients with tumor size <= 1.0 cm, 173 of 1196 (14.5%) patients with tumor size >1.0, <= 2.0 cm, and 265 of 852 (31.1%) patients with tumor size > 2.0, <= 3.0 cm. Among all 2268 patients, the percentages of lymph node involvement (pN1+ pN2) were: 47.6%, 47.2%, 24.0%, 18.9%, 18.1%, 0%, 0%, and 0% for solid predominant (Sol), micropapillary predominant (MIP), variants of invasive adenocarcinoma (VIA), papillary predominant (Pap), acinar predominant (Aci), lepidic predominant (Lep), minimally invasive adenocarcinoma (MIA), adenocarcinoma in situ (AIS), respectively. For Sol and MIP, the percentages of lymph node involvement were significantly higher than other subtypes, 50.0% and 66.7% in tumor size <= 1.0 cm, 42.0% and 38.6% in tumor size > 1.0, <= 2.0 cm, 52.2% and 55.7% in tumor size > 2.0, <= 3.0 cm. Conclusion: Our study revealed that lung adenocarcinoma subtypes had important role in lymph node involvement for the patients with small-sized lung cancer. (C) 2016 Published by Elsevier Ltd.