Archaeologists working in Catalonia, Spain, excavated a 1,600-year–old female skeleton and were surprised to find that she had a pelvic tumor. They were even more surprised to learn that the tumor had teeth! Such a thing is known as a teratoma and they are the first to document it in the ancient world. My friend Cris documented one photographically when she worked at a hospital and said that the surgeons rub their hands together with glee over what they will find inside. Also known as a dermoid cyst, this one was lined with black hair, had a full set of teeth, and a partial elbow. They result from the abnormal development of germ cells, and can even contain eyeballs. When they form what looks like a malformed fetus, they are sometimes mistaken for a parasitic twin. "Ovarian teratomas are bizarre, but benign tumors," writes lead researcher Núria Armentano, of the Universitat Autònoma de Barcelona. Even so, the benign teratoma may have killed the ancient woman by displacing other organs.