The blood supply of experimental liver metastases. IV. Changes in vascularity with increasing tumor growth

Vascularity of solitary Walker tumors implanted within the liver was studied in Holtzmann rats. Changes in arterial and portal vascularity were documented in tumors ranging in size from < 1 mm. to 33 mm. in diameter. Colored silicone rubber solutions were injected into the arterial and portal circulations in each animal, and specimens were studied under a stereomicroscope. The very smallest tumors (< 1 mm. in diameter) appeared as a blank space without any newly developed circulation. Tumors slightly larger, 1 to 2 mm. in diameter, induced the development of new vessels which encircled the tumor. These vessels were derived from either the arterial or portal circulation, or from both, which were mixing freely. All moderate-sized tumors, which were 3 to 7 mm. in diameter, had well-developed arterial circulations. Massive tumors, ranging from 7 by 8 mm. to 33 by 33 mm. in size, developed a wide variety of vascular patterns. These ranged, in a random fashion, from predominantly arterial to predominantly portal, as well as a combination of both vascular systems. Over-all vascularity varied from sparse to well developed. It is concluded that the pattern of vascularity of liver metastases is at least in part dependent on the size and growth of the tumors and that this vascularity is a continually changing phenomenon.