Please explain - it makes no sense to me...

How can an ovarian cancer be endometrial stromal sarcoma (low grade) if there was NO endometriosis found - ever - and the uterus had been removed about 20 years prior to this large tumor on the ovary - which, by the way, wasn't there a year ago????

I was told it is very rare (<1% of ovarian cancers), but it just does not make sense. How is this even possible???

[Naominjw]

Well, I feel silly answering my own question. ESS is a fraction of 0.2% of gynecological cancers, so as a primary ovarian cancer it is even more rare!  But I found an answer on a Johns Hopkins Pathology page: http://www.ovariancancer.jhmi.edu/sarcoma.cfm

So, it can actually be from a uterine sarcoma even if the hysterectomy was from the distant past.

Weirdly it says its behavior parallels advanced stage uterine ESS. That is hard to believe. And there doesn't seem to be any consensus on treatment.  

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