Well, I'll tell you this, if I'd known about the Pfizer vaccine on that side, in that arm - then I'd have said the same much earlier about it being the most likely cause. There is a thread on here that talks about just that, other people with lymph nodes in armpit up after the jab, glassgirl (a member) posted a link to raised lymph nodes under the arm AND in the breast being a possibility after the jab. Infact, they are even saying that women should tell radiographers if they have had the jab and are having a mammogram in the following weeks ! DId they ultrasound the 'thickened' area ?