Quantitative analysis of microvascular structure and function in the amelanotic melanoma A-Mel-3.

Blood cell velocity, capillary diameter, and capillary length were determined in the microcirculation of the amelanotic hamster melanoma A-Mel-3 as well as in s.c. tissue of tumor-free animals. Studies were carried out using a dorsal skin flap chamber, intravital microscopy, and television techniques after transplantation of a 0.5-cu mm piece of tumor tissue. The tumor revealed a special microvascular configuration of short, thin-walled, sometimes dilated capillaries running around the edge of the tumor. Large avascular areas appeared in the center part approximately 5 days after tumor transplantation. Although mean capillary blood cell velocity was not different in tumor-containing and tumor-free preparations, localized irregularities of blood flow were observed close to points of endothelial sacculations. Huge platelet conglomerates were consistently noted in capillaries of the tumor, blocking the blood stream temporarily. Due to discrepancies in microvascular morphology and lack of visible vascularization, large parts of this tumor seem to be inaccessible to tumor treatment. This implies that better vascularization of these regions might enhance the efficiency of cancer treatment. The chamber technique, intravital microscopy, and television methods combined with the subsequent, quantitative microvascular analysis may provide a unique means for direct evaluation of local therapy, particularly during early melanoma growth.