I too noticed the armpit odor for about a year before I was diagnosed. That was in 2010. I wish I would have remembered that, I have since been diagnosed with metastatic breast cancer with a possible 2 year prognosis. The smell never really went away. I started smelling it in my right armpit. I don’t have cancer on that breast but I have it in my lymph nodes in my neck and armpit on the right side. I had a left breast mastectomy and have a tumor in my left armpit and it has spread to my bones, liver and lymph nodes. My neighbors dog could smell my cancer. There is a smell. I have an acute sense of smell. I never thought it was cancer. Have it checked out. Don’t wait.