A mature cystic teratoma with teeth - a twin or not?

I have been chasing round the internet for six months now with a google alert for " mature cystic teratoma".  That means that I get links to pages that mention the term sent to my inbox. Every day I get an email with more than six links to articles about mature cystic teratomas but no one so far has suggested that this is an enclosed twin.

But womb twin survivors are tell me that they have a teratoma with teeth or hair, or other body parts visible and as far as they are concerned this is their twin.  Here is an example of an article written very recently on this subject: Is this a twin or not?

BMJ Case Reports 2012;

Rare disease

‘Teeth in the brain’ – a case of giant intracranial mature cystic teratoma

John O’Grady, Lina Kobayter, Chandrasekaran Kaliaperumal, Michael O’Sullivan

Department of Neurosurgery, Cork University Hospital, Cork, Ireland

The authors describe a case of a giant intracranial mature cystic teratoma in a 16-year-old girl presenting acutely with a severe headache, vomiting and a complex generalised seizure with a background history of intermittent headaches for 3 years. CT and MRI brain demonstrated a ruptured large cystic teratoma encapsulating two large teeth within the diffusely dense fatty heterogeneous lesion. Surgical debulking of the cyst was performed and the calcific remnants were left behind owing to dense adhesion to the brain. The procedure was complicated by postoperative hydrocephalus and needed a ventricloperitoneal shunt. She is currently asymptomatic and undergoing rehabilitation.

and another:

Ned Tijdschr Geneeskd. 2012;

[A woman with an unusual sonogram of the abdomen]. [Article in Dutch]

A 29-year-old female complained of abdominal swelling. Transvaginal sonography showed an unusual view of a cystic ovarian mass composed of various dense, round structures. A laparotomic right ovarian cystectomy was performed. The diagnosis was a mature teratoma or dermoid cyst, which is a benign germ cell tumor composed of differentiated, adult-type tissues. 

A "benign germ cell tumour"?  How many more terms must we chase to find an enclosed twin?

Have you ever had a dermoid cyst  or a mature cystic teratoma?  As far as you are concerned, does that make you a womb twin survivor?

What do you think?