Does a growing lump on a one-stage immediate breast reconstruction after mastectomy because of cancer followed by a tissue flap procedure meancancer?

Must get it checked. A new lump doesn't necessarily mean cancer, but you definitely must get it checked out to be sure. New lumps can appear after mastectomy and reconstruction, more with flap surgery than implants. More often than not, it is fat necrosis (hard fat) or scar tissue. Fat turns hard when the blood supply to that area isn't quite as good as it should be. Neither fat necrosis or scar tissue are harmful.
Not necessarily. It could be scar tissue, a problem with the implant or a fluid collection but you do need to see your doctor ASAP. Good luck.