You’ve seen them. Those grainy, slightly terrifying medical photos circulating on Reddit or "weird history" Twitter accounts that look like something straight out of a Cronenberg flick. A mass of tissue, pulled from an ovary or a tailbone, grinning back at the surgeon with a row of fully formed bicuspids. Maybe there's a clump of long, dark hair tangled in the mix. People call them "monsters," but in the medical world, they’re known as teratomas.
It’s weird. Really weird.
But here’s the thing: these aren't your twin you "absorbed" in the womb (usually). That’s a common myth that just won’t die. Instead, a tumor with teeth and hair images usually depicts a germ cell tumor that decided to go rogue and start building body parts it had no business building in that specific location.
What exactly are we looking at?
The word "teratoma" comes from the Greek teras, meaning monster. It’s a fitting name, honestly. Most tumors are just clumps of disorganized, fast-growing cells that don't do much other than take up space and steal nutrients. Teratomas are different. They are overachievers in the worst way possible.
Because they originate from germ cells—the "master cells" intended to create sperm or eggs—they are pluripotent. That’s a fancy way of saying they have the blueprints for everything. Your brain, your fingernails, your thyroid gland, even your eyelashes. When these cells become chaotic, they start executing those blueprints. They don't make a whole human, but they might make a patch of scalp or a molar.
I once talked to a pathology tech who described opening a dermoid cyst (a common type of mature teratoma) and finding it filled with a substance that looked exactly like "warm pancake batter and wet doll hair." It's visceral. It’s gross. But from a biological standpoint, it’s actually kind of a miracle of misdirected potential.
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The "Teeth and Hair" Factor: Why these specific parts?
Why do we always see teeth and hair? Why not a random spleen or a floating eyeball?
Actually, complex organs can happen, but they are incredibly rare. Hair and teeth are made of tough stuff—keratin and enamel. They survive the environment inside a cyst much better than soft, delicate tissues like lung or liver tissue would.
- Ectodermal dominance: Most benign teratomas favor the ectoderm, which is the embryonic layer responsible for skin, hair, and neurons.
- The Enamel Shield: Teeth are the hardest substance in the human body. Once they form, they don't just dissolve.
- The Sebum Soup: These tumors often contain sebaceous glands. These glands pump out oily "gunk" that preserves the hair inside the tumor, creating that specific, tangled look you see in the famous tumor with teeth and hair images that haunt the internet.
Sometimes, these tumors get even weirder. There are documented cases of "struma ovarii," a teratoma that is mostly made of thyroid tissue. This can actually cause the patient to suffer from hyperthyroidism because the tumor is pumping out thyroid hormones even though it's sitting on an ovary.
Mature vs. Immature: The stuff that matters
Not all of these "monsters" are equal. Doctors generally split them into two camps: mature and immature.
Mature teratomas are usually benign. They’re the ones with the teeth. Because the tissue is "mature" (it’s finished growing and differentiating), it’s mostly just a weird, structural nuisance. You cut it out, and the patient is usually fine.
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Immature teratomas are the ones that keep oncologists up at night. They contain embryonic-like tissue that hasn't figured out what it wants to be yet. These are cancerous. They grow fast and spread. Interestingly, these ones often don't have the well-defined teeth or long hair that make for viral photos, precisely because the cells are too disorganized to finish building those structures.
The Reddit Famous Cases
You might have seen the "molar in the brain" story. Back in 2014, a baby in Maryland had a brain tumor removed that contained several fully formed teeth. This wasn't a standard ovarian teratoma; it was a craniopharyngioma. It’s a reminder that these biological glitches can happen anywhere along the midline of the body—from the pineal gland in the brain down to the coccyx (tailbone).
In newborns, the most common site is the sacrococcygeal region. These tumors can be massive, sometimes larger than the baby itself at birth. Most are benign, but the sheer size requires incredible surgical precision to remove.
Why the "Absorbed Twin" Theory is mostly wrong
We need to address the "Fetus in Fetu" thing. It's a staple of daytime talk shows and clickbait.
Fetus in fetu is a condition where a malformed fetus is found inside the body of its twin. It’s incredibly rare—about 1 in 500,000 births. While a teratoma is a disorganized clump of tissues, a fetus in fetu usually has a visible axis, like a spine or limb buds.
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If you see a tumor with teeth and hair images, 99% of the time, it’s a teratoma. It didn't start as a person. It started as a cell that forgot its instructions. It's an important distinction because the "absorbed twin" narrative adds a layer of grief and "creepiness" that isn't scientifically accurate for the vast majority of patients.
Diagnosis and "Wait, is this inside me?"
Most people find out they have a teratoma by accident. You go in for a routine ultrasound or an MRI for back pain, and the radiologist sees a "complex mass."
On an X-ray, these tumors are surprisingly easy to spot if they have teeth or bone. Enamel is radio-opaque. It glows white. Finding a tooth in a pelvic X-ray is a "pathognomonic" sign—it basically confirms the diagnosis right there. No other tumor is going to grow a premolar.
Actionable Insights: What to do if you're worried
If you've stumbled upon these images because you’re researching a recent diagnosis, take a breath.
- Check the Pathology: The most important word in your report isn't "teeth" or "hair"—it's "mature" vs. "immature." Mature dermoid cysts are incredibly common, especially in women in their 20s and 30s.
- Surgical Consult: Most teratomas need to come out. Not always because they are "evil," but because they can cause ovarian torsion (twisting) or they can eventually rupture, which causes a massive inflammatory response.
- Blood Markers: Doctors often check for AFP (Alpha-fetoprotein) or hCG levels. These can help determine if the tumor is behaving more like a standard cyst or something more aggressive.
- Stop Doomscrolling: The images online are the extreme cases. Most teratomas are small, internal, and boring until a surgeon opens them up.
The fascination with tumor with teeth and hair images is human nature. We are hardwired to be repulsed and intrigued by "the uncanny"—things that are almost human but not quite. But beneath the shock value is a fascinating look at how our cells hold the potential to build every part of us, even when they lose the map.
If you or someone you know is dealing with a diagnosis, focus on the "mature" classification. In the vast majority of cases, these are just biological hiccups that, once removed, become a very weird story to tell at dinner parties—maybe after the appetizers are finished.
Next Steps for Patients and Researchers:
If you have been diagnosed with a dermoid cyst, schedule a follow-up with a gynecological surgeon to discuss a cystectomy. This procedure specifically removes the tumor while preserving the rest of the ovary. For those interested in the pathology, you can request your surgical "gross description" report post-op, which will detail exactly what types of tissue were found inside the mass. For medical students or the curious, the NIH PubMed database contains extensive case studies on "extragonadal teratomas" which explain how these cells migrate during embryonic development.