Metastatic potential of malignant fibrous histiocytoma of myxoid or giant-cell subtype in rats.

We have previously reported on the induction of rat malignant fibrous histiocytomas by 4-hydroxiaminoquinoline 1-oxide. The present study describes cell number- and time-related formation of metastatic lung nodules after i.v. injection of cell suspensions containing various numbers (10(3) to 10(5)/ml) of myxoid or giant-cell subtype malignant fibrous histiocytoma cells. The metastatic potential of the myxoid subtype of rat malignant fibrous histiocytoma was significantly enhanced by i.v. injection of tumor cells selected from metastatic lung nodules and was further increased by repeating the selection procedure more than 7 times. In contrast, the growth activity of subcutaneous transplants of tumor fragments obtained from metastatic lung nodules derived from myxoid subtype did not differ from that of parent malignant fibrous histiocytomas.