Metastasis via the blood stream: the method of intravasation of tumor cells in a transplantable melanoma of the hamster.

Tumor cells entered the vascular compartment of transplantable amelanotic melanoma of the hasmster 3 days after transplantation, closely following vascularization of the transplant. Examination of the tortuous giant capillaries at the edge of the transplant showed tumor cells breaching the thin endothelium of these vessels. Extravasation of red cells into the surrounding tumor tissue and attempted haemostasis by small platelet aggregates attached to the vessel walls were also found.