A miniature brain, along with partially developed skull bone and matted, greasy hair were found in a teenager's ovaries, when she was undergoing a routine appendix surgery in Japan.
Teratomas, also known as dermoid cysts, are not uncommon. However, ones that have brain-like structures are extremely rare, according to surgeons Shiga Medical Centre for Adults in Japan.
The surgeons also found and removed a tumour they noticed growing on the ovaries of the 16-year-old patient during a routine appendectomy.
Subsequent analysis of the tumour showed that the tumour contained a teratoma with a brain-like structure along with a partially developed skull bone and hair fragments.
The teratoma, which is Greek for the word monster, held a brain-like structure that was so advanced it had partially developed into a cerebellum with a brain stem and was able to transmit electrical pulses delivered by the research team.
The tumour was about 10 centimetres wide and held a mat of greasy hair and a brain-like structure that was covered by skull-like bone material.
Teratomas are actually a type of tumour that develop most often in organs such as the thyroid, liver, lung, brain and ovaries - their defining characteristic is the development of bodily material that is out of character for the location in which it is found.
Like cancerous tumours, they result from a malfunction during cell division, often in ways that resemble abnormal stem-cell growth.
Such tumours can cause symptoms due to the immune system being activated, but the patient in this case had no symptoms before her surgery and recovered quickly after removal of both appendix and tumour, the researchers said.
The details of the case was published in the journal Neuropathology.
