Effect of the size on the transplantability and lethality properties of spontaneous and transplanted mammary tumors in mice.

It is well known that the fate of transplanted tumors is controlled by the genetic relationship be tween the host and the tumor used for transplanta tion. This c@ncept has been accepted since the work of Little, Strong, Bittner, and others, as it has been reviewed by Bittner (1, 2), Little (5), Gorer (4), and Snell (9). In a study of some aspects of the growth of spontaneous and transplanted mammary tumors submitted to various experimental conditions, it was noticed that the transplantability, defined as “theability of a tumor to grow in a homologous host,― as well as lethality, defined as “theability to kill the host,― might be different, depending upon the size of the tumor at the time of its trans plantation. Browning (8), working with either heterologous or homologous transplantations made by trocar in the anterior chamber of the eye, showed that in spontaneous tumors in mice, “autonomy― was not present in small tumors but appeared gradually with increasing age of the tumors. In this study we have attempted to study the transplantability and lethality properties of spon taneous, as well as of transplanted, mammary tu mors in mice, when inoculated at different sizes.