Experimental evidence in support of the dormant tumor cell.

When rats were injected intraportally with as few as 50 Walker-256 carcinosarcoma cells aarcoma cells and then examined 5 months later for hepatic tumor growth, none was evident. If, however, 3 months after injection the rats were subjected to repeated laparotomy and liver examination at 7-day intervals, 100 percent had a tumor within a few weeks.