A dead fetus has been removed from the stomach of a four-year-old boy after he complained of pain in West Bengal, India. A CAT scan revealed, what was suspected as a tumor to be a dead foetus inside his abdomen.

“The dead embryo which had hands, legs, nails and a partially formed head was removed from the child’s body after a long operation,” Dr Shirshendu Giri told International Business Times. “The boy is all right now, still under close observation.”

Doctors said the boy suffered from the rare medical condition, “fetus in foetu” (baby within a baby), in which a malformed foetus is found in the body of its twin. In the early stages of pregnancy, one of the twin foetuses may absorb the other. The enveloped twin becomes a “parasite” that relies on its host.

The abnormality has an incidence of one in 500,000 live births, with less than 100 reported cases worldwide, according to a 2005 case report in ANNALS Academy of Medicine Singapore.

In June 2009, a man in India named Sanju Bhagat underwent surgery to have a parasitic twin, which he carried inside his body for 36 years, removed. In March 2006, doctors in Pakistan removed two foetuses from inside a two-month-old girl.