Fetus in fetu, or FIF, is an extremely rare condition where the body of a living twin houses the remains of an undeveloped sibling. This condition occurs in 1 of 500,000 live births and only 200 cases have ever been documented in medical literature. FIF is usually found in young children of the male gender.

However, a 17-year-old girl from India has just recently been diagnosed with FIF. This particular case has a rarity that is simply unprecedented, as it is only the eighth reported case found in an adult and the first ever case reported to be found in an adult woman.

The girl sought medical attention stating that a lump had developed in her abdomen and that she had been experiencing intermittent, abdominal pain for about five years and that sometimes when she ate she became full rather quickly.

After the initial examination, doctors only felt a hard, odd-shaped lump in the girl's abdomen and after tests came back normal, they performed a scan.

"An abdominal contrast-enhanced computed tomography (CECT) scan showed a well-defined mass that measured approximately 25 by 23 by 15 centimeters, roughly 9.8 by 9.1 by 5.9 inches, extending from epigastrium [just above the stomach] to upper pelvis," they wrote in their case report.

"It was showing fat density areas, soft tissue and multiple calcified density components of various sizes and shapes resembling the shape of vertebrae, ribs and long bones. This mass was causing displacement and compression of adjacent abdominal viscera."

Due to their findings, doctors then scheduled an operation to remove the mass.

The doctors successfully removed what they described as a mass made from "hairy cheesy material, multiple teeth and structures resembling limb buds," including fat, cartilage and bone, as well as neural, intestinal and skin tissue.

While the patient says she is feeling better, yearly check-ups are required to ensure that any remaining tissue doesn't become cancerous.

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