I wasn’t I wasn’t told about cording or lymphodema either until I discovered the cording. I wore the sleeves every day and massaged the area where I had lumpectomy AND the area below where cording was. Two breast care physios showed me exercises for each. Lymphodema involves raising my arm (left) for half an hour whilst masssging under arm, and breast snd surrounds. Working outwards from the breast and down the arm and down from ribs.
For the cording I held the arm out loosely and rested wrist on chair or ??? Hard rubbing or massaging under the arm and under breast. In same position work the hand up and down through wrist.
other one is bend arm in and put hand behind base of neck - then stretch your elbow up and back.
Do the same with the arm straight. Stretch up as far as possible and as far back till it hurts.
By the way I was so rigorous my lymphodema has settled snd I don’t have to wear the sleeves. And the cording is nowhere to be seen now. I can still feel it but can’t see the cording. Good luck.