Enhancement of leukemia and mammary tumor development in ICRC mice with subcapsular graft of neonatal thymus.

Weanling ICRC mice were given a syngeneic graft of neonatal thymus. The control (C) and experimental mice (IT) were observed for their natural death. Neoplasms of the reticular tissue developed in 80% (19/23) mice of IT group and 21% (5/23) in control. Mammary tumors developed in 52% (12/23) in IT group and 35% (8/23) in controls. Cell of origin of the leukemia was reticular in 9/23, lymphocytic in 7/23 and mixed lesion in 3/23 in IT group; while in controls it was 2/23 and 3/23, respectively and mixed lesion was absent. All mammary tumors were of adenocarcinoma series.