It says that the cells still form tumors occasionally. Are there any plans to deal with that?

I have not got the betta cell form human embryonic cell is still form tumors occasionally.
The human embryonic cell differentiates to betta cells is not successful directly. However, they differentiate the huamn embryonic cell to pancreatic endoderm and implanted these still-immature cells into mice. Eventually, the mice without their own betta cell can produce insulin. I think they get no information about the right signal to differentiate the huamn embryonic cell to betta cells. However, it is a great result.