Desperate medical tourists who go abroad for injections of stem cells run the risk of ending up with tumors made of someone else’s cells.

That’s what happened to Jim Gass after he had a stroke in 2009. Gass, the former chief legal counsel at Sylvania, traveled to Argentina, China, and Mexico to get injections of fetal tissue that he hoped would heal him.

Now in a case study published in the New England Journal of Medicine, doctors at Brigham and Women’s Hospital report that Gass ended up with “a strange sticky fibrous growth” in his spine. And the cells weren’t his.

“It looked like nothing I had ever seen,” John Chi, director of neurosurgical spine cancer at the Brigham, told the Boston Globe. “It was stuck onto the nerves and had an odd consistency.”

The bizarre result is being described as a “cautionary tale” to anyone seeking treatments from fly-by-night clinics offering miracle cures in countries with few regulations. And it’s not the first such case, either. In 2009 doctors reported a brain tumor in a child whose parents had taken him to Russia for injections of human fetal cells.

What’s sickening is that Alphabet, the owner of the Google search engine, is partly to blame for the quackery. Searching “stem cell treatment” in Google has for many years returned paid ads for shady clinics in Panama and elsewhere that promise to cure autism, cerebral palsy, and just about anything else with a dose of mystery cells.

The reason such stem cell treatments aren’t offered in the U.S. is that there is no evidence they work, and they would not be able to pass review with the Food and Drug Administration. Gass apparently spent as much as $300,000 on the treatments and travel expenses.

After his stroke, Gass had to walk with a brace and a cane, he told the New York Times. That’s when he began doing research online, finding clinic websites and stories of how pro golfer and former San Francisco 49ers quarterback John Brodie had apparently been helped by fetal stem cells.

Other NFL players have allowed their names to be used in advertisements for sketchy orthopedic treatments involving injections of bone marrow, which are offered in the U.S. (see “The NFL Has a Problem with Stem Cell Treatments.”)

After getting an injection of fetal cells in Mexico, Gass began suffering sharp back pain. That is when doctors found the strange mass growing near his spine. He’s since had radiation treatment to try to remove it.

Gass told the Globe he still thinks that stem cell treatments are promising. “I couldn’t accept where I was. A life lying down in bed is not the place to be,” he said. “The consensus was stem cell therapy was going to be the future of treatment for stroke. I read all the cautionary tales even though I didn’t believe them.”

Read more: NEJM, Boston Globe, New York Times