Please ask your oncologist to schedule a breast ultrasound fir that breast & underarm area since you may have developed a seroma which is a collection of fluid that can be removed via needle drainage if particularly bothersome. I developed a seroma 18 months after my lumpectomy & it is rather small so we're just watching it. I also have persistent breast lymphedema most likely from my radiation treatment. Lymphatic massage did nothing & I am living with it. Just joyful to go on with my life.