lump in opposite breast after mastectomy

It's YOUR body and you have every right to be concerned as having had breast cancer makes you more prone to a second one. Get a mammogram, ultrasound and the most definitive of them all, a biopsy. I did the same thing as you...didn't take the tamoxifen because of SE and two years later, second primary in other breast. Had another mastectomy. It was 8mm, grade 3, no LVI, and hormone +, so now I DO take my tamoxifen and realize that any SE can often disappear once your body gets used to it. I didn't need chemo either. So, even if it is cancer, get it early as possible. The "pea-sized" lump is enough to look for, but I believe cancer tends to be hard and fixed...but cancer is a strange entity and has no fixed rules. Try not to be so afraid. Unlike mine, most of the time the second cancer bears a resemblance to the first in every way but still remains a primary rather than a recurrence, which oddly is a good thing. And, you may be jumping the gun and it could be perfectly benign.....but get it checked. I am always amazed that doctors do not recommend further investigations of breast lumps. My friend kept getting "oh it's nothing" for three years and ended up with stage 4 when, by the very nature of her cancer, she could have caught it early when in was curable. Makes me mad as hell.