“The word Teratoma comes from the Greek words “teras” and “onkoma” which appropriately translate to “monster” and “swelling”. It is believed the bizarre tumors come from germ cells, which form human eggs, and is caused by wayward sperm or eggs that erroneously activated. The result is an encapsulated tumor, with tissue or organ components resembling a fetus – that attempts to become as human as it can.” – From source
We can file this in the bizarre but true category. The human body is truly amazing in it’s capacity to adapt and we know so little about it. These are yet another example of that grotesque ability to adapt and even mutate.