Large animal model for retroperitoneal lymphatic and lung metastasis

Retroperitoneal lymph node and lung metastasis are important prognostic factors for gynecologic cancer. The present study aimed to develop a new animal model for retroperitoneal lymph node and lung metastasis. VX2 squamous cell carcinoma tumor tissues were injected into the left gastrocnemius muscle of 38 healthy female New Zealand white rabbits. Animals were randomized into three groups according to day of sacrifice: 1, day 19; 2, day 22; and 3, day 25. Implanted primary tumor (IPTu), left and right retroperitoneal lymph node volumes and lung wet weights were measured on the day of sacrifice. The IPTu and left and right retroperitoneal lymph node volumes increased in a time-dependent manner. In addition, the proportion of animals with metastasis to the left peritoneal lymph nodes and the number of nodes involved increased over time. For days 19, 22 and 25, the proportion of animals with nodal metastasis was 58.3, 84.6 and 100%, respectively, and the number of affected nodes (range) was 3 (2–3), 3 (3–5) and 4 (4–5), respectively. No metastasis was detected in the right peritoneal lymph nodes. Metastasis to the lungs also increased with time, but was not statistically significant at days 19, 22 and 25 with metastasis present in 33.3, 38.5 and 76.9% of animals, respectively. Rates of metastases to the left retroperitoneal lymph nodes and lungs were found to positively correlate with the volumes (r=0.416 and 0.449, respectively). The current study assessed the characterization of a rabbit VX2 carcinoma model. This animal model is likely to be useful for evaluating retroperitoneal lymph node and lung metastasis.