Background: During the past two decades, many studies have sought to find reliable predictors of N0 status in small-sized lung cancers. However, the way of tumor size measurement was usually not clearly stated, and controversy remains as to whether systematic lymph node dissection should be performed in patients with subcentimeter tumors.
Methods: We reviewed correlations between lymph node involvement and clinicopathological variables in 243 small peripheral non-small cell lung cancers with their size measured in fresh specimens before formalin fixation. Histologic subtypes of adenocarcinomas were classified in line with the new International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) lung adenocarcinoma classification.
Results: Incidence of N1 and N2 nodal involvement was 5.3 and 6.6 %, respectively. N2 disease was present in a proportion of subcentimeter tumors (2/53, 3.8 %). No lymph node metastasis was revealed in squamous cell carcinomas, adenocarcinoma in situ, minimally invasive adenocarcinoma, lepidic predominant adenocarcinoma, or invasive mucinous adenocarcinoma. Collectively, the five cell types accounted for 34.6 % of all the small peripheral cases.
Conclusions: Precise measurement of tumor size in fresh tissues revealed that tumor size was not a reliable predictor of N0 status. However, through histologic classification, systematic lymph node dissection might be avoided in more than one third of small peripheral NSCLC.