Experimental study of lymphogenous peritoneal cancer dissemination: migration of fluorescent-labelled tumor cells in a rat model of mesenteric lymph vessel obstruction.

Primary gastrointestinal cancer frequently spreads to the mesentery, omentum and other parts of the peritoneum, and these deposits are generally considered to be induced by intraperitoneal seeding from the primary lesion. However, a few peritoneal metastatic cases or cases with positive intraperitoneal lavage cytology, without serosal infiltration, have been reported. Most of peritoneal dissemination is certainly attended with serosal involvement of gastrointestinal malignancy. Nevertheless, we observe an unusual case of peritoneal dissemination without definite serosal invasion of the malignancy. And peritoneal dissemination is likely to be concomitant with lymph node metastasis in both cases with and without definite serosal invasion. In this study, we examined peritoneal cancer dissemination from the viewpoint of lymphogenous metastasis. For the model of lymphatic invasion, we established an animal experimental model of mesenteric lymph vessel obstruction. With these models, lymphangiographical studies were made on the fourth postoperative day (ten animals each) and we obtained mesenteric lymphangiograms of extensive mesenteric lymph vessels and reflux of lymph distal to the obstruction point from all ten animals. Next, in these experimental models, fluorescent-labelled tumor cells (rat hepatoma cell line, N1-S1) were infused from the mesenteric lymph node distal to the obstruction point on the fourth postoperative day (five animals each), and the migration of these tumor cells was investigated via fluorescent micrography. Subsequently, the fluorescent-labelled tumor cells were revealed in the mesenteric lymph nodes, mesenteric lymph vessels, interstitial tissues of the mesentery, submucosal lymph nodules and mucosal layer of the small intestine. Hence, lymphatic invasion and obstruction may cause extensive peritoneal dissemination via the lymphatic route.