A tumour containing a miniature brain has been found growing on the ovary of a 16-year-old girl in Japan.
The 10-centimetre-wide tumour was discovered when the girl had surgery to remove her appendix. When doctors cut the tumour out, they found clumps of greasy, matted hair inside, and a 3-centimetre-wide brain-like structure covered by a thin plate of skull bone.
Closer analysis revealed that it was a smaller version of a cerebellum – which usually sits underneath the brain’s two hemispheres. A mass on one side resembled a brain stem – the structure that normally joins to the spinal cord.
