I have had stage 3 breast cancer, later I had a fatty tissue lump removed from under my arm.  It has grown back and the underarm is sometimes swolledn and tender. My cancer surgeon says it is nothing to worry about and they have ultrasounded the area twice now. (the surgery was 2 years ago) is this a sign of cancer again?
Hi and welcome to Chat Doctor. It isn't usual sign of cancer relays. If surgery was performed adequately then there should be axillary lymph node malignancy.  It can be resulting from previous surgery and disorder in lymphatic or venous flow. Or it can be subcutaneous infection. Ultrasounds would notice any strange lumps and also needle aspiration and biopsy can be performed.  Wish you good health.