About one-fifth of ovarian tumours contain foreign tissue, including hair, teeth, cartilage, fat and muscle. These tumours, which are normally benign, are named teratomas after the Greek word “teras”, meaning monster. A fair description given the grim medical oddity discovered when a sixteen-year-old girl went into surgery to have her appendix removed.
During the procedure, doctors found a 10-centimetre-wide tumor and so doctors decided to remove the anomaly. To their surprise, when they examined the tumor they found that it had matted hair, a thin plate of skull bone, and a 3-centimetre-wide brain-like structure. It was so complete it even had a cerebellum, a part of the brain at the back of the skull in vertebrates, which functions to coordinate and regulate muscular activity.. A mass on one side resembled a brain stem and the miniature brain even developed in such a way that electric impulses could transmit between neurons.
Brain cells are often found in ovarian teratomas, but it is extremely unusual for them to organise themselves into proper brain-like structures. So far medical science has yet to definitively define what causes ovarian teratomas, one competing theory is that they arise when immature egg cells mutate and turn rogue, producing different parts of the anatomy. Interestingly though, this one though seemed to be of sound mind.