Relationship between micropapillary component and micrometastasis in the regional lymph nodes of patients with stage I lung adenocarcinoma

Aims: To determine whether a micropapillary component is a prognostic predictor, with particular reference to nodal micrometastasis, in patients with stage I lung adenocarcinomas. Methods and results: Thirty-five cases with stage I lung adenocarcinomas, obtained from lobectomies or pneumonectomies, and 434 dissected hilar and mediastinal lymph nodes, were retrospectively reviewed. A micropapillary component and nodal micrometastasis were found in 16 (45.7%) and 14 (40%) of the 35 cases, respectively, with nodal micrometastasis in 24 (5.5%) of the 434 lymph nodes, in an immunohistochemical study using an anti-cytokeratin antibody. Ten (62.5%) of the 16 cases with a micropapillary component, and four (21.1%) of the remaining 19 cases, showed nodal micrometastases (P = 0.014). Kaplan-Meier survival curves demonstrated that there was no significant difference between the cases with and without a micropapillary component (P = 0.28). However, the 5 years' survival of the cases with and without nodal micrometastases were 71.4% and 35.7%, respectively (P = 0.03). Conclusions: A micropapillary component may be a manifestation of aggressive behaviour, as shown by frequent micrometastasis, for stage I lung adenocarcinomas.