My lump wasn't external - I didn't know they could be external - but I was misdiagnosed initially too. The doctor who looked at my mammogram and ultrasound said I had a lump of necrotised (dead) fat. I thought I was off the hook but GP said I should see a surgeon just to be sure. Core biopsy then showed up mucinous cancer. It was a big shock but surgeon said it was a non-aggressive cancer that didn't usually spread and that I probably wouldn't even need chemo. As you might have found yourself when you google mucinous cancer you get sites that tell you it rarely spreads to other parts of the body, is slow growing etc. So I thought, okay I've got cancer but it's sounds like the best type of cancer to get.
Then I had my surgery and I was told my cancer was grade 3 (aggresive) and there was DCIS too. So I've had to have the chemo, due to start rads on Sept 24 and after that the tamoxifen. I guess I still feel kind of lucky as my cancer hadn't spread to my lymph nodes but still....I feel like I will forever have to be on guard now - questioning the doctors, keeping as informed as I can, watching my diet etc etc etc. It certainly gives you a new appreciation of your health!