What Doctors Discovered Wedged Inside This Woman's Brain Will Make You Shudder

Let’s just say it had teeth.

Last week, Hrayr Shahinian, M.D., a neurosurgeon at the Skull Base Institute in Los Angeles, performed a first-of-its-kind surgery to remove a tumor deep inside the brain of a 26-year-old Ph.D. student from Indiana. When it was completely extracted from her patient's head, Shahinian was surprised to find that the the tumor was embryonic—and get this—it had hair, bones, and teeth. What?!

We spoke with Shahinian to find out more about what the heck that thing was and how it got in his patient's brain to begin with.

What the Eff Is That Thing?
The tumor turned out to be a teratoma tumor, which means "monster tumor" in Greek, says Shahinian. Apparently, it picked up this name because it usually contains random body parts like limbs, eyes, hair, teeth, bones, and can even take a fetus-like structure, he says. These suckers are very rare. Shahinian says the probability of one occurring is somewhere around one in the tens of millions. But when they do occur, they typically pop up near a person's tailbone, in the ovaries, or in the testicles. Having a teratoma in your brain is extremely rare, he says.

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How Did It Get All Up in Her?
When you're just a wee little embryo, these tumors can form as your cells begin dividing to form a fetus. Sometimes, a genetic mutation can force some of the germ cells—the cells that create your hair, nails, bones, and other parts of your body—to form a tumor. That tumor is formed before you're even born and continues to grow with you, he says. "It's not like one embryo absorbed the other one—it was there all along," says Shahinian. And fun fact—the tumor can start out with baby teeth that grow into fully-developed adult teeth.

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So Was That Ball of Body Parts Her Twin?
Teratomas have been called twins because they sometimes take the form of a fetus, and they share the same DNA as the person carrying them. However, technically, it's not a twin. Plus, since this is a tumor we're talking about, the mass can be cancerous. Luckily, this young woman's wasn't. Today, she's back at home and will make a full recovery, says Shahinian.