New, simple model of mesenteric lymph node metastases in the rat.

Injection of 1 x 10(6) CC531 colonic carcinoma cells into the mesenteric lymph nodes of Wag/Rij rats resulted in the growth of tumors within the lymph nodes. These were apparent after 3 days, whereas lung and liver metastases were not observed until 5 weeks after inoculation. In vivo labeling with bromodeoxyuridine (BrdU) followed by immunostaining with an anti-BrdU monoclonal antibody showed a marked difference in the proportion of labeled cells of the metastases at different times after inoculation: after 3 days, many tumor cells but also many stromal cells were labeled; after 7 and 11 days, however, far less stromal cells were positive, most labeled cells being tumor cells.