Fig. 1

Histopathological examination of the inoculation site of NOD SCID mice injected with hUC-MSCs (HE staining, 10 ×). A Animals in Group 1 were euthanized, and no obvious abnormalities were seen at the inoculation site. B Animals in Group 2 were euthanized, and tumor nodules with central necrosis were observed at the inoculation site. C–H Animals in Groups 3, 4, 5, 6, 7, and 8 were euthanized. The stem cell mass at the inoculation site was necrotic, and the surrounding tissues exhibited fibroblastic proliferation accompanied by lymphocyte infiltration