Medial regression and its functional significance in tumor-supplying host arteries. A morphometric study of hepatic arteries in human livers with hepatocellular carcinoma.

Livers from 30 patients with hepatocellular carcinoma were submitted to morphometric analysis of the arterial smooth muscles to correlate the peculiar circulation in cancer, i.e., the lack of flow regulation, with the structure of blood vessels in and around the tumors. The anatomical radius and medial thickness of the cross-sectioned arteries were determined in a standardized state of the circularly stretched, internal elastic membrane. It was shown that not only the medial smooth muscles were extremely hypoplastic in arterioles contained in the carcinoma, but the media of tumor-supplying host arteries was also significantly thinner than in the controls, even in segments distant from the tumor, showing more or less lowered regulatory activity of the whole tumor-bearing arterial tree. Under these circumstances, dissection of the host arteries was frequently found to arise, evolving into the typically non-muscularized tumor vessels. The authors consider the abnormal hemodynamics of cancer to be fully explainable from these vascular alterations.