It looks to be about as painful as it sounds too. Below and on the left is a picture of the 4-month old infant with the rapidly growing tumor (right before surgery); on the right is a picture of the girl at seven years of age (way after the surgery).
As the authors state:
The case we report was entirely benign, did not relate to vital structures and had no intracranial extension.This made it possible to surgically remove the tumor without there being permanent damage to any vital function. As you can see from the images below, even the bones of the face were distorted by the growing mass.
A teratoma is the kind of tumor that I study in mice. We have a mouse model for testicular teratomas. These mice have a mutation in a particular gene that renders the protein made from that gene to not work. This causes misregulation of the germ cells (the cells that colonize the gonad and eventually give rise to sperm in the testis). In this particular mouse, the misregulation leads to a teratoma.
Teraomas have long fascinated biologists by their ability to grow incredibly fast and show amazing signs of organization and differentiation. They are thought to arise from very powerful, or pluripotent, cells such as germ cells. In this case, instead of colonizing the gonad, a germ cells got off course and wound up in the head and neck region. Normally if this kind of misguidance happens the cell can't survive and dies off. But sometimes (rarely) it doesn't die off, and instead begins to grow and develop outside of the proper environment. Overall, teratoma formation is a relatively rare sort of tumor, especially in the face.
Nevertheless, this demonstrates the power of the cells that make up your germline and give rise to your gametes. Remember that gametes (spermatocytes and oocytes) combine to give rise to the next generation. That power is harnessed very carefully by nature, and sometimes things go wrong. This study is a case in point.