The development of a vascular bed is essential for solid tumour growth and
metastasis, In many rumours, mean vascular density can be related to the ra
te of metastasis and, therefore, to prognosis. In other tumour types, such
as cutaneous melanoma and head-and-neck squamous cell carcinoma, this relat
ion is absent. Until now, the reason for this has been unclear, but since t
hese particular tumour types are also known for their propensity to spread
via the lymphatic system, it may be speculated that the presence of a pre-e
xisting lymphatic bed and the formation of new lymphatics (lymphangiogenesi
s) are important factors, Growth factors involved in lymphangiogenesis duri
ng embryogenesis have been recently identified and these are also expressed
in many tumour types, but the existence of tumour-induced lymphangiogenesi
s has not so far been reported. Partly, this could be due to the lack of re
liable endothelial markers, thereby hampering a consistent evaluation of ly
mphatic vasculature, This editorial discusses the role of the lymphatic bed
in mediating the metastasis of solid rumours, summarizes known methods to
detect lymphatics, and proposes a hypothetical mechanism of tumour-induced
lymphangiogenesis, Copyright (C) 2000 John Wiley & Sons, Ltd.