Like all the fingers on your hand, the signs and symptoms of breast cancer are different for everyone. Some individuals may not even have any initial signs of breast cancer.
One symptom of breast cancer is a mass or lump on the breast or under the arm (in the armpit). The lump may or may not be noticeable with the naked eye. However, the lump may be detected during your breast self-exam (BSE), medical exam or mammogram. According to the Breast Cancer Foundation, "Nearly 70 percent of all breast cancers are found through self-exams and with early detection the 5-year survival rate is 98 percent."
Eight out of ten lumps found in the breast are non-cancerous. The lump may be a cyst or infection and not necessarily breast cancer. However, if you find a lump, contact your primary care physician immediately.
https://www.empowher.com/breast-cancer/content/breast-cancer-signs-and-symptoms