Abstract: Background and purpose: The lymph node metastatic model of rectal tumor is a useful tool for the research on tumor occurrence, development, metastasis and antineoplastic therapy. There are few reports about establishment of larger animal model. This study aimed to establish feasible and reproducible lymph node metastatic models of VX2 tumor in rabbits. Methods: The VX2 tumor tissue was put into the puncture needle. The VX2 tumor tissue in the needle was orthotopically transplanted into the rectal wall of the New Zealand white rabbits successfully. Twenty New Zealand white rabbits were transplanted. Two experimental rabbits were scanned by MR weekly. Tumor growth curve and lymph node numbers were observed on MR. Experimental rabbit tumor volumes were measured by MR post-processing software. The rectal tumor and surrounding lymph nodes were resected, and the specimens were fixed. The sections were stained with HE. We explored the relationship between tumor volume and growth time, the number of metastatic lymph nodes and tumor volume, respectively. Results: Thirteen models were successfully established with a rate of 65%. Tumors limited in the rectal wall were observed on the fourth week. Tumor size increased over time. There was significant difference in the tumor volume between different periods (growth cycle number) (F=52.865, P<0.05). There was a significantly positive correlation between tumor volume and the growth cycle number (r=0.910, P<0.05). The metastatic lymph nodes could be observed when VT>9 cm3. The number of metastatic lymph node increased obviously from the ninth week. The more tumor volume, the greater the number of metastatic lymph nodes was observed (F=92.531, P<0.05). There was a significantly positive correlation between the number of metastatic lymph nodes and the tumor volume (r=0.945, P<0.05). Conclusion: Metastatic lymph node models of VX2 tumor in New Zealand white rabbits were established successfully. This model has some value in the research on local growth, invasion mechanism, lymph node metastasis and biological characteristics of rectal cancer.

Key words: Model, Rectal cancer, Metastatic lymph node