@LoveFall
6 years ago, I had a Mucinous Borderline Tumour - not nearly as rare as yours. It extended as far as a full term pregnancy, was taking up most of my abdomen and weighed over 2 kilos. I had the usual debulking - hysterectomy, Fallopian tubes, ovaries, omentum and was told I was Borderlines are 'cured by surgery' and I have a more chance of being hit by a meteorite or run over by a London bus as any further problems. But I would be monitored for 5 years with scans and bloods, just in case. I was told all this by a top gynaeoncological surgeon at St Thomas' in London. 'Only a small percentage recur and only a small percentage of that percentage will have turned into cancer'.
It used to be very controversial as to whether Borderlines should be classified as cancer or not. They used to be called tumours of Low Malignant Potential and then the WHO pronounced and said Not Cancer, because they're not invasive, just sit on top of an organ and grow v-e-r-y slowly and hardly anyone dies of them.
They grow so slowly that chemo kills off your good cells long before if affects Borderline cells and ends up by killing more patients than it cures.
All the UK NHS/Charity websites (except Ovacome) have followed the WHO advice, but you do occasionally come across a doctor - particularly Ob-Gyn, who doesn't have any advanced oncological qualifications and is still going by what they learned at Med School 30 years ago. My local hospital is a case in point, but fortunately they refer to St Thomas'.
I don't know if Brenner Borderlines behave differently. It's good that you're seeing a gynaeoncologist. You could ask what they would call it and about management going forward.
I know it's only a word, but the treatment and outlook for Borderlines is entirely different - and it matters v much to me, and probably you?, whether they call it cancer or not.
If you want to learn more, MDAnderson in Houston seems to be the authority on Borderlines in general. I don't think the sample of recorded Brenner Borderlines is really big enough to draw any conclusions as yet.
I hope you don't think I'm dissing your Canadian hospital. My cousin lives in Toronto and I'm v envious of their routine colon cancer screening for the over-60's(?) Wish we had it here.