I've been in my job since August. A couple of days after joining, I retweeted some tweets from my new organisation from my personal-but-only-used-for-work Twitter account (I use it to tweet about issues related to my profession, but as myself).
In an earlier Tweet I'd mentioned my partner's profession, as it's related to mine and was relevant to the discussion I was having. My colleague who monitors the Twitter account saw my previous tweet, and when I got in the next morning said 'so you're dating a [name of profession], that's handy!' So I said yes, I was, and no, we aren't married, and yes, we've been together a while, and yes, it's handy for work.
Next thing I know, colleague is telling everyone about 'LittleA's boyfriend' who is this handy professional.
My partner is female. I was brand new in the organisation and I'm quite private and didn't really want to go round to everyone and tell them my partner is female as my first introduction. So I smiled and nodded and said 'my partner is indeed a X'.
It's now been going on for about 9 months and it's gone on far too long now and is way too entrenched for me to pipe up and say 'oh actually, I don't have a boyfriend, my partner is a woman.'
One day soon though I'm going to be asked for a name, or to invite 'him' into work for 'his' handy expertise and it's going to be a whole world of awkward.