ANGIO-TUMORAL COMPLEX IN HUMAN-MALIGNANT MELANOMA CHARACTERIZED BY FREE LAMININ - ULTRASTRUCTURAL AND IMMUNOHISTOCHEMICAL OBSERVATIONS

Neo-vessel density in primary rumours as a prognostic factor for metas tasis has been questioned. For this reason we have investigated qualit ative aspects of tumour vascularity and particularly the association o f cancer cells with endothelium, focussing on the peri-endothelial mat rix. We have examined the matrix between endothelium and tumour cells in human invasive and metastatic malignant melanoma using transmission electron microscopy and immunohistochemistry. We have identified a hi therto unrecognised image (the angio-tumoral complex) in which the tum our cell and endothelium are in direct contact via an amorphous matrix . This amorphous matrix lacks an organised lamina and contains predomi nantly laminin with noticeably less collagen type IV. In this image en dothelial cells showed no signs of physiological damage, no tumoral in travasation, and tumour cells occupied a pericytic location. This typi cal image was absent from naevi. We regard the laminin in this amorpho us matrix as 'free' laminin as distinct from laminin integrated into a n organised lamina. We discuss the role of this free laminin in promot ing the migration of melanoma cells in contact with vessels and sugges t the possibility that this angio-tumoral complex represents a marker for metastasis.