Doctors find 'twin' growing inside 17-year-old girl's stomach

For five years, a teenager in India couldn't figure out why she had a noticeable, hard lump on her stomach that seemed to keep growing. When doctors first examined her, they assumed it was a tumor, but they later discovered it was a malformed twin, which had been growing inside her abdomen for the last 17 years.

The twin had hair, teeth and a spine according to the British Medical Journal (BMJ) study published on August 12.

While this may sound like a one-off medical miracle, the teen actually has an incredibly rare condition called fetus in fetu (FIF).

FIF occurs in 1 out of 500,000 live births, and fewer than 200 cases have been reported since its initial discovery in the early 19th century. This case is particularly interesting to researchers because most of the previous cases were detected in boys during their childhoods.

This is only the eighth case of adult FIF, and the teen is the oldest known female in the world to be diagnosed with it.

The doctors were able to successfully remove the 12-by-6-by-4-inch mass — the largest FIF ever removed — from the girl's body.

"I was much worried about my abdominal lump," she said in the BMJ report. "After my operation I am feeling very well and my abdomen is now flat and my parents are also very happy. Thanks to all operating doctors."

The teenager is now in full recovery and making regular follow-up visits to doctors.

Check out the Geobeats video above to see the CT scans of the fetus.