Nodal occult metastasis in patients with peripheral lung adenocarcinoma of2.0 cm or less in diameter

Background. Detection of occult micrometastasis in regional lymph nodes is crucial for diagnosis and selection of appropriate therapy for patients wit h pN0 nonsmall-cell lung carcinoma. Using immunohistochemical staining, we evaluated the impact of detection of occult micrometastasis on the prevalen ce and prognosis of patients with lung adenocarcinoma of 2.0 cm or less in diameter. Methods. A total of 103 pN0 disease patients with peripheral lung adenocarc inomas of 2.0 cm or less in diameter were enrolled in this study: We studie d 1,438 regional lymph nodes for occult micrometastasis by immunohistochemi cal staining for cytokeratins. Results. Micrometastasis was detected in 49 lymph nodes (3.4%) of 21 patien ts (20.4%) but not in patients with localized bronchioloalveolar carcinoma or localized bronchioloalveolar carcinoma with foci of collapse of alveolar structure. The 5-year survival rate (61.9%) of patients with micrometastas is was significantly (p 0.0041) lower than that of patients without microme tastasis (86.3%). Conclusions. There still remains a risk of nodal micrometastasis in patient s with primary peripheral lung adenocarcinoma, even if the diameter of the tumor is smaller than 2.0 cm. Selection of patients for limited surgery sho uld be done prudently, talking into consideration the risk of nodal microme tastasis.