Pattern of spread of bloodborne tumour.

The pattern of bloodborne tumour spread has been studied experimentally in syngeneic rats. A variety of tumour types has been injected intravenously, intraportally and also intra-arterially via the left ventricle. Tumour cell arrest as a factor in the localization of metastases in the lung following intravenous injection of cells, and in the liver following intraportal injection, is emphasized. Once tumour cells have entered the arterial circulation they disseminate to almost all organs in similar proportions to the distribution of cardiac output. The dissemination and arrest of cells is not found to correlate with the later distribution of metastases. For example, certain organs (especially the adrenals) which receive only low fractions of injected cells, are always preferred sites for bloodborne metastasis. A strikingly similar pattern of 'arterial metastasis' is also seen for all the tumours used despite their very different histological and biological natures.