A Teratoma is a a tumour that collects cells from around the body. Known to have hair, fingernails, teeth and sometimes limbs, eyes and other body parts (I always think of The Dark Half by Stephen KIng). Some of them used to be mistaken for a vestigial twin. Teratoma translates to Monster Tumour and it certainly is!
I started making Teratoma’s after watching a documentary them and have spoken to many teratoma patients. Unfortunately a Teratoma can cause some severe problems when in the brain (if the patient survives a brain Teratoma-often a baby at birth).
Teratoma’s are also commonly found on the Ovary at puberty (failed menstruation) or at the base of the spine.
I do not recommend doing a google image search for Teratoma.