A convenient murine model for the study of intra-abdominal lymph node metastasis

Lymph node metastasis is one of the most important prognostic factors for cancer patients. There are few animal models of lymph node metastasis. The purpose of this study was to develop a simple animal model without surgical trauma. B16F10 melanoma (1 x 10(6) cells in 0.1 ml phosphate-buffered saline) were slowly injected into the retroperitoneal space followed by direct puncture at the position between the anus and tail of 50 female C57BL6 mice. At 1-week intervals for 4 weeks after the procedure, we examined the retroperitoneal tumor and intra-abdominal lymph nodes. There was no morbidity and no mortality. At 2 weeks after inoculation, the retroperitoneal tumor was visible macroscopically at the position between the rectum and the sacrum, and histological examination showed the occurrence of intra-abdominal lymph node metastasis in all mice. The number of positive nodules was increased and was affected by the amount of cancer cells inoculated and the interval from inoculation to lymph node metastasis. A convenient murine model for the study of lymph node metastasis has been developed. Our animal model does not involve surgical trauma and may be useful in the analysis of the association between surgical stress and lymph node metastasis and in the elucidation of the mechanism and prevention of lymph node metastasis.