Lymphatic invasion of micropapillary cancer cells is associated with a poor prognosis of pathological stage IA lung adenocarcinomas

The cancer cells of lung adenocarcinoma with a micropapillary pattern (MPP) have been found to frequently invade lymphatic vessels, and the prognosis of patients with lung adenocarcinoma with an MPP is poor. In the present study, the cancer cells of lung adenocarcinomas containing an MPP were found to express vimentin more extensively than those in lung adenocarcinoma without an MPP. The contribution of cancer cells in the MPP component to adenocarcinoma lymphatic invasion was assessed using vimentin as a marker. Vimentin expression was analyzed in the cancer cells present in each lymphatic vessel and compared with the expression of vimentin in the cancer cells in the adenocarcinomas without an MPP component. The results showed that the cancer cells in the lymphatic vessels expressed vimentin more extensively than those in the adenocarcinoma components without an MPP, suggesting that cancer cells derived from an MPP component are present in the lymphatic vessels. By contrast, the area of the MPP component in each adenocarcinoma was <25%. These findings suggest that cancer cells in MPP components have a high capacity to invade lymphatic vessels and that their high invasive capacity may be associated with a poor prognosis in patients with adenocarcinoma with an MPP component.