The operative wound from a radical mastectomy should be thoroughly healed within 5-6 weeks after the
operation. However, tissue around the mastectomy site, including the
arm on the same side of the mastectomy, can swell and accumulate fluid (edema). This is because a lot of blood vessels and lymph vessels located in the armpit get severed or damaged during the procedure. This prevents blood and lymphatic fluid coming from the skin and arm to properly drain into the heart.