Fate of intravenously injected cultured human cancer cells in the lungs of congenitally athymic nude mice.

Three cultured cell lines of human lung cancer with varied degrees of thromboplastic and fibrinolytic activities were injected subcutaneously or intravenously into congenitally athymice nude mice, and their fate was observed with light and electron microscopes. All the cell lines formed solid tumor masses at the sites of subcutaneous injection. When the cancer cells with high or moderate thromboplastic activity were injected intravenously, marked platelet aggregation and fibrin deposition, followed by neutrophilic infiltration, were seen around the cancer cells arrested in pulmonary arterioles or capillaries. Platelet aggregation and fibrin deposition were less conspicuous, when the cancer cells with low thromboplastic activity were injected. No metastatic foci were found 2 weeks after the intravenous injection of each cancer cell line. These results suggest that thromboplastic activity of human cancer cells is closely related to thrombus formation at the sites of lodgement and that thrombus develops without participation of immunological mechanisms.