Scanning electron microscopy study of the blood supply of human colorectal liver metastases

https://doi.org/10.1016/j.ejso.2003.08.009Get rights and content

Abstract

Aims: The failure of hepatic artery directed treatment of colorectal liver metastases may reflect a major portal venous contribution to tumour blood supply. This study provides ultrastructural details of the blood supply of colorectal liver metastases and their association with the portal vein and hepatic artery.

Methods: Resected liver specimens from six patients with colorectal liver metastases were examined by histology and scanning electron microscopy (SEM), following vascular resin casting.

Results: Nine metastatic colorectal adenocarcinomas were identified. The main feature of all tumours on SEM was direct communication between hepatic sinusoids and tumour vessels. A direct portal venous connection with tumour vessels was observed in a single specimen, whilst a direct arteriole connection was not identified.

Conclusions: It appears that both the hepatic artery and portal vein contribute to the blood supply of colorectal liver metastases through sinusoidal connections with tumour specific blood vessels. SEM provides useful additional information on the morphological features of tumour vasculature.

Introduction

Tumour embolization, chemotherapy and selective internal radiation via the hepatic artery are used to treat selected patients with unresectable colorectal liver metastases, with the intention to improve survival and provide palliation.1., 2., 3., 4., 5., 6., 7. These treatment modalities are based on the assumption that colorectal liver metastases have a predominant hepatic artery blood supply. Although occasionally providing local tumour control; cure or improved survival is uncommon. Recurrences eventually occur in more than 80% of patients, usually at the tumour periphery.3., 4., 5., 6., 7.

The relative contribution of portal vein and hepatic artery to the blood supply of colorectal liver metastases is controversial. Various techniques are described for assessing tumour blood supply including direct histological assessment, dye injection, angiography, Doppler ultrasonography, resin casting and tracer studies.8., 9., 10., 11., 12., 13., 14., 15., 16. There are however very few studies that provide comprehensive morphological assessment of the vasculature of human colorectal liver metastases. Scanning electron microscopy (SEM) is one technique that allows detailed morphologic assessment of tumour vasculature. This study evaluates the blood supply of human colorectal liver metastases by histology and SEM.

Section snippets

Materials and methods

Nine human colorectal metastases were obtained from hepatic resection specimens. All available blood vessels were cannulated and irrigated with warm heparinised saline (10 IU/ml) (Weddell Pharmaceuticals, NSW, Australia) until the effluent was clear. The specimens were further irrigated with warm saline containing heparin (10 IU/ml) (Weddell Pharmaceuticals, Sydney, NSW, Australia), papaverine (12 mg/ml) (David Bull laboratories, Melbourne, VIC, Australia) and 6% polyvinyl pyrollidone (PVP40)

Results

All tumours were evaluated (Table 1). Specimens 1–5 were solitary tumours from different patients, whilst specimens 6–9 were tumours obtained from one patient with multiple metastases.

Discussion

Tumour related angiogenesis is critical to the growth of metastatic tumours.18 Tumour proliferation requires the formation of tumour specific blood vessels, which in the liver can potentially develop from the hepatic artery, portal vein or sinusoids.10., 11. Targeting tumour blood supply forms the basis of many therapeutic strategies in patients with unresectable colorectal liver metastases.

The hepatic artery has long been considered the predominant source of blood supply to colorectal liver

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