I’ve always understood that most healthy women have breasts that vary in shape and size. Maybe this is something you never thought of until now. Surely the lumpectomy is the explanation and you couldn’t have expected no change unless you also had reconstruction. But even there, it won’t work perfectly as you’re on anastrozole which affects the hormones and any reconstruction would be unaffected (I assume).
I struggle with neuropathic pain in my ribs and remaining breast muscle from my mastectomy/FAC and treatment 3 years ago. I’m grateful I don’t have to think about my absent breast much any more. Mastectomy bras are too uncomfortable so I go monoboobed and, if people stare, tough. But I’m not you and this is obviously important to you.
You could consider corrective surgery but do you want to go through all that again for something you say is imperceptible except to you? Where is your secondary cancer? What treatment are you on? Things like that might well affect how you feel about your body now. I’d suggest you promise yourself not to look and compare (it’s like poking and prodding the original lump, as if willing it to go away) and just be glad it’s not noticeable when you’re clothed.
I was told - somewhat offhand, so I wouldn’t take it as a certainty - that radiotherapy can cause breast shrinkage. I had mine very young and went on (over more than a decade!) to be overall much, much larger than I was at that point, and ended up out by about a cupsize between the treated and not treated sides. It did indeed seem the least of my worries! And, despite the much larger difference thank you’ve noticed, I can tell you that no one else ever noticed in the slightest, at least while I was dressed.
I know the feeling of just wanting your body back to how it was, but you’ve been through life-saving treatment. Changes are somewhat inevitable, and I hope you can let go of this and accept it as a relatively small price for what you’ve been through.
Before I had my lumpectomy my surgeon explained to me that the breast would be slightly higher afterwards, because - and I’m sorry I can’t remember the technical details - the overall effect was like having a breast lift, which some people actually pay to have done for cosmetic reasons. He then said that later on he could do the other breast to match, if I so desired.
I looked at him in total disbelief, and said that was very kind of him, ad the NHS, but I would never choose to inflict surgery on my body unless strictly medically necessary, that I was just grateful not to be losing my breast, and that I really didn’t care if looked slightly different after the operation, as long as it was no longer trying to kill me…
And ten years later, my breasts do look slightly different, but I’m still alive (for the time being, anyway).
My advice would be to focus on gratitude here. It’s not great that breast cancer treatment is such a series of physical and mental assaults, in fact it’s all hugely distressing, but the doctors inflict it, and we endure it, in order to save our lives.