Skin cells have been shown to be pluripotent embrionic stem cells, that means given the right hormonal baths, or implantation into a uterus, they have the same chance of being an olympic sprinter (are only olympic athletes human?) as a fetus.

Your tumor arguement also fails. You consider it a "malfunction" primarily because a tumor has adverse health impacts on the host woman - but so does a fetus.

And neither can grow without taking advantage of the blood, nutrition and hormonal functions of the host woman. Again, what is the biological difference?

Your "take off from the mother" sets the "independence" point as birth. Which is fine - I agree, once the fetus is born, it is independent.

but you have not made the case for the biological independence of the fetus in a manner that is differentiated from a tumor and pluripotent skin cells.