A routine surgery at Zhejiang University Hospital in China turned into a groundbreaking medical discovery when doctors found an embryonic twin complete with hair and teeth growing inside a 16-year-old girl’s brain. The case, documented in 2023, represents one of the most complex examples of a rare condition known as fetus in fetu occurring in the brain.
The teenage patient, whose identity remains protected for privacy reasons, had been experiencing recurring headaches and vision problems for several months before seeking medical attention. Initial scans revealed what doctors believed to be a standard tumor, but the surgery unveiled a far more extraordinary situation.
Dr. Wei Mei, the lead neurosurgeon involved in the case, described the discovery during the operation. “What we found was unprecedented in my 25-year career,” said Dr. Mei. “Inside the tumor-like mass were developed tissues including bone, hair, and several fully formed teeth. It was essentially the remains of a twin that had been absorbed during early fetal development.”
The condition, technically termed intracranial fetus in fetu (iFIF), occurs in fewer than 1 in 500,000 births worldwide. The presence of such a formation in the brain is even rarer, with only a handful of documented cases in medical literature. The mass, measuring approximately 4 centimeters in diameter, had been growing slowly since birth but only recently began causing symptoms.
The surgical team successfully removed the entire mass during a complex eight-hour procedure. Dr. Mei explained the delicate nature of the operation: “We had to proceed with extreme caution. The mass was intertwined with crucial blood vessels and brain tissue. One wrong move could have caused catastrophic damage.”
The patient’s parents, who wished to remain anonymous, shared their initial shock at the diagnosis. “When doctors first explained what they found, we could hardly believe it,” the girl’s father told local medical reporters. “To think that our daughter had been carrying her twin in her brain all these years is something that still amazes us.”
The case has sparked significant interest in the international medical community. Dr. Sarah Chen, a neurological specialist at Stanford University who wasn’t involved in the case but reviewed the findings, highlighted its significance: “This case provides invaluable insights into fetal development and the potential complications of twin pregnancies. It also demonstrates how seemingly routine symptoms can sometimes lead to extraordinary medical discoveries.”
The teenage patient made a remarkable recovery following the surgery. Three months post-operation, she reported complete resolution of her headaches and vision problems. Follow-up scans showed no signs of regrowth or complications.
The case has been documented in detail in the Chinese Journal of Neurosurgery, providing important reference material for future similar cases. The surgical team emphasized that their success was partly due to advanced imaging technology that allowed for precise surgical planning.
Dr. Mei and her team have since established a new protocol for examining unusual brain masses in young patients. “This case teaches us to never make assumptions,” she noted. “What appears to be a routine tumor could be something far more complex.”
The hospital has incorporated this case into their teaching curriculum, using it to train new neurosurgeons about the importance of thorough examination and the potential for unexpected findings during surgery.
Editor’s Note: This article is based on medical records and reports from Zhejiang University Hospital, peer-reviewed articles in the Chinese Journal of Neurosurgery, and interviews with the medical team. The case has been verified by multiple independent medical institutions and published in international medical journals.