Histologic study on the metastatic process in the experimental model of lymph node metastasis

The process of lymph node metastasis was studied in an experimental model that was successfully established in our laboratory. The model O-1N carcinoma was transplanted to the buccal pouch of 60 hamsters, and seven or eight hamsters were killed every week from 1 to 8 weeks for histologic examination. At 3 weeks, neoplastic invasion of vascular spaces was demonstrated, and early stage lymph node metastases were seen in five of seven animals. At 5 weeks, lymph node metastases were more advanced, and lung metastasis occurred in one animal. At 8 weeks, lymph node metastases were seen in all eight animals and lung metastases were seen in two of them. Tumor cells initially seen as clusters in afferent lymphatic vessels and in the peripheral sinuses gradually spread to the medulla, replaced the entire lymph node, and extended into adjacent extranodal tissue. The process of metastasis closely resembled that seen in human oral carcinomas.