Objective: We sought to determine the critical diameter of a peripheral non-small cell lung cancer tumor less than which no evidence of nodal micrometastasis is present.
Methods: Samples of 3081 lymph nodes from 181 patients with stage I peripheral lung cancer (155 with adenocarcinoma and 26 with squamous cell carcinoma) who had undergone complete resection with systematic lymphadenectomy were used in the study. In the samples immunohistochemical staining for cytokeratin was performed. The expression of vascular endothelial growth factor (VEGF) at primary sites was also immunohistochemically assessed.
Results: Nodal micrometastasis was detected in 44 patients. The mean tumor sizes were 2.2 +/- 1.3 cm (range, 1.0-7.0 cm) in nodal micrometastasis-positive adenocarcinoma, 2.1 +/- 0.9 cm (range, 0.5-6.0 cm) in nodal micrometastasis-negative adenocarcinoma, 4.8 +/- 2.3 cm (range, 2.2-10.0 cm) in nodal micrometastasis-positive squamous cell carcinoma, and 3.2 +/- 2.1 cm (range, 0-9.0 cm) in nodal micrometastasis-negative squamous cell carcinoma. The tumor size in the nodal micrometastasis-positive group tended to be greater than that in the nodal micrometastasis-negative group in squamous cell carcinomas, but there was no significant difference in adenocarcinomas. Nodal micrometastasis was not found in patients with squamous cell carcinoma of 2.0 cm or less in diameter. However, nodal micrometastasis was found in 20% (19/95) of the patients with adenocarcinoma of 1.1 to 2.0 cm in diameter and even in 4 of 11 patients with adenocarcinoma of 1.0 cm or less. Among the patients with nodal micrometastasis, survival of patients with vascular endothelial growth factor overexpression was worse than that of patients without it. The survival of patients with nodal micrometastasis without vascular endothelial growth factor overexpression was comparable with that of patients without nodal micrometastasis.
Conclusion: A limited surgical intervention without lymphadenectomy is validated for squamous cell carcinoma of 2.0 cm or less without pleural involvement. In adenocarcinoma the tumor size itself is not a reliable guide for nodal micrometastasis status. In patients with nodal micrometastasis with vascular endothelial growth factor overexpression, the risk of systemic disease should be considered.