Decrease in the incidence of malignant ileo-caecal immunocytoma in LOU/C rats after surgical removal of the ileo-caecal lymph nodes.

Malignant ileo-caecal immunocytomata, which secrete immunoglobulin, frequently arise spontaneously in LOU/C/Wsl rats. The tumors are confined to the ileo-caecal region and could originate either in the wall of the caecum or in the ileo-caecal lymph nodes. After excision of the ileo-caecal lymph nodes, the incidence of the type of tumor was found to be reduced significantly. The results strongly suggest that the first cells to undergo malignant transformation are located in the ileo-caecal nodes.