The vascularization of liver metastases. Histological investigation of gelatine-injected liver specimens with special regard to the vascularization of micrometastases.

The vascularization of 19 human livers with metastases was investigated using gelatine perfusion and resin corrosion techniques. (1) In 16 livers examined after injection via the hepatic artery hypervascular metastases were demonstrated in 12 cases, hypovascular in 4. (2) Injection via the portal vein showed that more than 50% of liver metastases had a distinct portal blood supply to the tumor periphery. In approximately one-third of cases the portal blood supply extended centrally. (3) Injection via the hepatic vein demonstrated venous drainage from peripheral areas of tumor in less than 30%, and from central areas in only 9%. Larger branches of the hepatic vein were not detected within metastases. (4) Tumor thrombi were seen within branches of the portal vein situated 1-1.5 cm from the tumor periphery in more than 50% of all liver metastases-suggesting the possibility of local hepatic retrograde tumor spread via the portal vein. (5) Central necroses were seen in hypervascular metastases only, mainly in tumors larger than 1-1.5 cm. (6) The incidence and vascularity of human hepatic micrometastases was investigated. Micrometastases were seen in close proximity to about 40% of the macrometastases. Metastases up to the size of 200 micron received their main blood supply via sinusoids. Neovascularization of tumors larger than 200 micron was demonstrated.