Nodal occult metastasis in patients with peripheral lung adenocarcinoma of 2.0 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 with pN0 nonsmall-cell lung carcinoma. Using immunohistochemical staining, we evaluated the impact of detection of occult micrometastasis on the prevalence 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 adenocarcinomas of 2.0 cm or less in diameter were enrolled in this study. We studied 1,438 regional lymph nodes for occult micrometastasis by immunohistochemical staining for cytokeratins. Results. Micrometastasis was detected in 49 lymph nodes (3.4%) of 21 patients (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 micrometastasis was significantly (p = 0.0041) lower than that of patients without micrometastasis (86.3%). Conclusions. There still remains a risk of nodal micrometastasis in patients with primary peripheral lung adenocarcinoma, even if the diameter of the tumor is smaller than 2.0 cm. Selection of patients for limited surgery should be done prudently, taking into consideration the risk of nodal micrometastasis.