Invasion of the hepatic capsule by tumour metastases to the liver.

Liver metastases of Waler 256 tumour in rats and of C3HBA tumour in mice were produced by mesenteric vein inoculation of tumour suspensions. Gross liver nodules were examined by light microscopy and by transmission and scanning electron microscopy. Subcapsular tumour nodules were seen to penetrate the hepatic capsule in all animals and to lodge on the peritoneal surface. Penetration occurred by stretching and attrition of the thin hepatic capsule in these animals. Studies done on human hepatic metastases revealed a different picture. In only a small number of such cases did peritoneal involvement occur from subcapsular nodules, and in these the penetration was limited, apparently by way of capsular veins and lymphatics. The thick fibrous capsule of human liver appears thus to form a barrier to peritoneal tumour dissemination.