This is an example of a sacrococcygeal teratoma [sa-crow-cock-sa-jeal
tear-a-toma], which is a tumor that affects roughly one out of every 35,000
births. The tumor is composed of "germ cells" which are supposed to become
part of the reproductive system, but in this case have become tumorous.
Such large teratomas are largely a danger during delivery, or from the blood
system of the tumor monopolizing too much of the baby's circulatory system.
Often surgeons will remove the tumor while the baby is still in the womb,
or deliver the baby by caesarian and operate afterwards.