A mom said she had a cyst with teeth and hair in her uterus. It's not as rare as you might think.

• A mom went viral on TikTok after finding out she had a cyst with hair and teeth in her uterus.
• The growth was a dermoid cyst, which are common, a doctor said.

When TikToker @Sandwitchbread, who goes by the name Page, started having unexplained bleeding and abdominal pain, she worried that she might be pregnant. She said in a TikTok video that she took a few pregnancy tests that came back negative, but she was still experiencing symptoms, so she reached out to her gynecologist. When the doctor saw her ultrasound, Page was in for a big surprise.

"It's not a baby," she said in a video that has been liked more than a half-million times. "It's something way worse than a baby."

Page said that the doctor told her that she had a seven-centimeter, chicken-egg-sized dermoid cyst in her uterus, as well as a smaller pea-sized cyst. Although the cysts are relatively common, hers had some unusual features: hair and tooth tissue.

The cyst likely started when Page was pregnant with her son more than two years ago, she said her doctor told her.

"For those of you who don't know what a dermoid cyst is, it's a cyst that grows hair and teeth and comes from particles of fetal tissue being separated during the development of a fetus," she said. "For about two years now I've had particles of my son, who I gave birth to, growing in my uterus."

Strange, but not uncommon

Dermoid cysts occur when tissue grows within an enclosed sac during fetal development. The cells in a dermoid cyst are embryonal, meaning that they "can demonstrate any final tissue type," said David Lagrew, MD, the executive medical director for women's services at Providence St. Joseph Hospital in Orange County, California.

That means cysts can contain hair and teeth, or even bone, Lagrew said.

In most cases, dermoid cysts appear on the head and neck, and they're often diagnosed at birth or within the first five years of life.

Usually, the cysts occur on the developing fetus when the cells became trapped in a sac. But in Page's case, the cells were likely from when her son was a fetus, she said.

The truth is stranger than fiction

Lagrew thinks that stories about dermoid cysts often garner attention because the idea seems so far-fetched.

"They've always created a stir, given the description and nature of these tumors," he said. "This is just another story of nature being weirder than we can make up."

Even within the medical community, the cysts are often the butt of jokes, especially since they're usually harmless.

"We always kid around saying the diagnosis can be made by placing an ice pack on the abdomen and listening for the teeth chattering," Lagrew joked.

Page's story — complete with a picture of the cyst featuring black hair and what appear to be teeth — took TikTok by storm. The video has more than 13,000 comments.

"That's wild, I've never even heard of this," one commenter said. "You learn something new every day."

Another put it more bluntly: "This sounds like the beginning of a horror movie."

"I'm a little too stunned to speak," Page said in her video.