Well, here is the list of users who were desysopped "for cause".  That is, they weren't desysopped because of a clearly compromised account, because of inactivity, because they died, or resigned, or they changed accounts, or they "vanished". 

There are only 33 names on that list and, as far as I can tell, only one of them identified as being a woman.  To be honest, I looked at that list and found it a bit disturbing that I've actually met at least 10 of those desysopped admins (they were all male).  Kinda made me wonder about the company I keep.  ;-)

As to how many are approved without a clear knowledge of their gender identity?  Probably most of them.  There are, without doubt, a lot of administrators assumed to be male who are actually female; the actual number is hard to determine, but I'd estimate at least 50, particularly amongst admins who don't frequent "drama" areas or participate in real-world activities. 

For the record, I was widely assumed to be a male editor up to and even including my RFA. I made the decision to "come out" as a woman just so the nomination pronouns would be accurate and nobody would think I'd pulled the wool over anyone's eyes.  And even still...the first vote to oppose my candidacy referred to me with "he" and "him" all the way through - as was pointed out by several other RFA participants  ("did you even read the nomination???")  This is a bit of a longwinded way of saying that, at least up until 2008, it was generally assumed that all RFA candidates were male unless they had disclosed otherwise. 

Risker/Anne