INDIA -- "About that lump in your abdomen. It was likely your unborn twin."
That's what a teenager in India was told after surgeons removed "hairy, cheesy material" from her abdomen two years ago, LiveScience reported.
More precisely, the mass measuring 14 by 6 by 4 inches contained apparent ribs and vertebrae along with "multiple teeth and structures resembling limb buds," per an analysis in BMJ Case Reports.
The 17-year-old had complained about a growing abdomen lump that sometimes caused her pain or the feeling of being full. After a CT scan, doctors diagnosed her with fetus in fetu, a rare condition in which an oddly developed fetus is found inside a person's body. Why it occurs is unclear.
Scientists say it's probably one identical twin absorbing another during early pregnancy, per Arizona State University, or a kind of tumor called a teratoma that's comprised of body tissues like muscle, bone, and hair.
Fewer than 200 instances are on record, and only seven in people who are 15 and older. In the Indian teen's case, doctors successfully removed most of the mass, but had to leave some tissue that was tightly bound to blood-supplying vessels.
That raises the chance of cancer and means she must be checked annually. But for now, the report says she's fine: "I was much worried about my abdominal lump," she says. "After operation I am feeling very well … and my parents are also very happy."