Prognostic Implication of Predominant Histologic Subtypes of Lymph Node Metastases in Surgically Resected Lung Adenocarcinoma

The International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society (IASLC/ATS/ERS) proposed a new classification for lung adenocarcinoma (AD) based on predominant histologic subtypes, such as lepidic, papillary, acinar, solid, and micropapillary; this system reportedly reflects well outcomes of patients with surgically resected lung AD. However, the prognostic implication of predominant histologic subtypes in lymph nodes metastases is unclear so far. In this study, we compared predominant subtypes between primary lung tumors and lymph node metastatic lesions in 24 patients with surgically treated lung adenocarcinoma with lymph node metastases. Additionally, we analyzed prognostic implications of these predominant histologic subtypes. We observed several discordance patterns between predominant subtypes in primary lung tumors and lymph node metastases. Concordance rates were 22%, 64%, and 100%, respectively, in papillary-, acinar-, and solid-predominant primary lung tumors. We observed that the predominant subtype in the primary lung tumor (HR 12.7, P = 0.037), but not that in lymph node metastases (HR 0.18, P = 0.13), determines outcomes in patients with surgically resected lung AD with lymph node metastases.