Lump in armpit

Jalsmama55

Hi everyone, I posted this is the "concerned about recurrence" area but thought I should post here too because I'm wondering about scar tissue from rads. So here it is. I was diagnosed 8/10, BMX 9/10, chemo 10/10-1/11 and 38 rads to my right side only. Left only had LCIS so mastectomy was more than enough to deal with that issue. Anyway, here's my concern, found a small knot/lump last night under cancer side armpit, up towards the top about 2 inches down from the shoulder crease. The lump is on the muscle/tendon that runs along my outer chest under my armpit.. It's a little bit bigger than the head of a pen. Hope that description makes sense Haha! I've already confused myself. The lump is a little painful and is really hard like a cyst and isn't movable. Anyone had anything like this in the means of scar tissue? Seeing rads onco tomorrow (I'm just more partial to him rather than onco) and he's extremely thorough and I figured if he wants a scan, he can take care of it right away. I'm so concerned that this could be a recurrence