Hi, Jemma - sorry to hear about your mum, after all she's been through already, hope in her case it is benign.
Anyway I was diagnosed with breast cancer nearly 3 years ago, when I was 49. (So I am older than your mum now which makes me feel very old!) I'd been having regular mammograms anyway because of breast cancer in the family and was due to go for one when I found a lump myself - was just sitting at the table in my nightie with my left hand in my right armpit (like you do!) when I felt it, went to GP pretty promptly, was referred on to breast clinic sooner than scheduled, had mammogram 1, mammogram 2 and needle biopsy all at once and was told it was malignant - bit of a shock, I'd had a fibroidenoma (sp?) before and assumed it was another.
This was mid-October 2000, I had lumpectomy early in Nov, there were 2 lumps in fact - one at the back by the chest wall, hadn't felt that one - they were relatively large and fast-growing and "hormone-receptor-negative" which meant having chemo and radiotherapy and not tamoxifen.
Had the chemo Jan-Jun 2001 - 12 doses - not too bad, the kids were great, older ones sorted out younger ones in the morning when I was too weary to get up, lost most of my hair but all over so still had a bit, no nausea but terrible mouth ulcers. Then had 4 weeks of daily radiotherapy in August - summer didn't really happen for us that year - normally it would be 3, but because of the chest wall tumour they hadn't been able to leave as big a margin as they like to around it so I had the extra week where they aimed the machine at that.
Since then, touch wood, no more problems - technically in remission I suppose but after 2 years of 3-monthly check-ups (alternately between the breast-care consultant and the oncology consultant) I have now graduated to 6-monthly. As far as I'm concerned I "had" cancer and am cured but you don't know, do you.
Also, in June 2001, after the chemo but before the radio, I had a pulmonary embolism - blood clot in lung - very painful and scary but my GP was wonderful, I called the HC and he was on the doorstep 10 minutes later, with his hypodermic in his hand almost (gave me diamorphine, "Harold Shipman's drug of choice" he said, what a wonderful bedside manner! It is lovely stuff though) - had 8 days in hospital for that, having heparin injections (and missed the only decent weather that summer!) and then the next 6 months on warfarin. I believe blood clots are a common complication of cancer/surgery although I don't think They know exactly why - or if They do They never told me.
Since having cancer myself I've heard of loads of people who've survived decades so there's lots of reasons to be optimistic.
Best wishes to your mum and you - if you would like to email me via mumsnet please do!