cT1aN0M0 lung adenocarcinoma treated with left S9+10 segmentectomy followed by completion lobectomy for a solitary metastasis (isolated tumor cells) in the neighboring segmental lymph node.

A 47-year-old woman with a lung adenocarcinoma of 1.3 cm located in the left S9+10 was treated by S9+10 segmentectomy with sentinel node (SN) identification using radioisotopes. During segmentectomy, frozen section of the segmental nodes at S9+10 and S6, identified as SNs, did not show metastasis; however, postoperative immunohistochemical staining with cytokeratin revealed isolated tumor cells in the segmental node at S6. None of the other dissected nodes, including the hilar, interlobar, and mediastinal nodes, showed metastasis, even with immunohistochemical staining. Completion lobectomy was conducted 6 days after segmentectomy, and the resected specimens did not show further metastasis. The final pathological diagnosis was adenocarcinoma with pT1aN0(i+)M0 stage A. The present case was indicative of the importance of dissecting the segmental lymph node located not only at the tumor-bearing segment but also at the neighboring segment, especially the one located between the primary tumor and the lobar bronchi.