Brain and skull found inside teen girl's ovary

In an unusual medical case, a 16-year-old girl was found to have a tumor containing hair, tissue resembling brain matter, and a skull-like, bony shell.

The discovery made by a team of doctors in Japan was described in a recently published study which calls the brain-like mass "well-differentiated and highly organized."

The team encountered the nearly 4-inch wide tumor on the girl's ovary during routine appendectomy.

According to New Scientist, when doctors cut the tumor after removing it, they determined that it had similar attributes to a small cerebellum and brain stem.

The Independent notes, "[Tumors] found on ovaries are normally harmless, though the cause of them is still unknown. Brain cells are often found in these growths, but it is very unusual for them to arrange into brain-like structures.

The patient is said to have "recovered well."