What is Breast Cancer
"Breast cancer is a cancer that starts in breast tissue. It happens when cells in the breast change and grow out of control. New cells grow even when you don't need them, and old cells don't die when they should. These extra cells can form a mass called a tumor.
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Sometimes the cancer does not spread any further. This is called "in situ." If the cancer spreads outside the breast, the cancer is called "invasive." It may just spread to nearby tissues and lymph nodes. Or the cancer may metastasize (spread to other parts of the body) through the lymph system or the blood.
Breast cancer is the second most common type of cancer in women in the United States. Rarely, it can also affect men."
What Causes Breast Cancer?
"We don't know what causes each case of breast cancer. But we do know many of the risk factors for these cancers. We also know that normal breast cells can become cancer because of changes or mutations in genes. Hormones also seem to play a role in many cases of breast cancer, but just how this happens is not fully understood." - American Cancer Society
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"To determine the extent of an individual’s breast cancer and if it has spread outside of the breast, the cancer is assigned a stage upon diagnosis. The early detection of breast cancer through annual mammography and other breast exams is the best defense against receiving a late-stage breast cancer diagnosis. Generally speaking, the earlier the cancer is detected, the greater the likelihood of a successful outcome." - National Breast Cancer Foundation
How gene changes can lead to breast cancer:
"Genes control how our cells function. They are made up of a chemical called DNA, which comes from both our parents. DNA affects more than just how we look; it also can influence our risk for developing certain diseases, including some kinds of cancer.
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Normal cells have genes called proto-oncogenes, which help control when the cells grow, divide to make new cells, or stay alive. If a proto-oncogene is mutated (changed) in a certain way, it becomes an oncogene. Cells that have these mutated oncogenes can become cancer.
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Normal cells also have genes called tumor suppressor genes, which help control how often normal cells divide in two, repair DNA mistakes, or cause cells to die at the right time. If a cell has a mutated tumor suppressor gene, then the cell can turn into cancer.
Cancers can be caused by gene changes that turn on oncogenes or turn off tumor suppressor genes. Changes in many different genes are usually needed to cause breast cancer.
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Some gene changes (mutations) are inherited or passed to you from your parents. This means the mutations are in all your cells when you are born.
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Most gene mutations linked to breast cancer are acquired. This means the change takes place in breast cells during a person's life rather than having been inherited or born with them. Acquired DNA mutations take place over time and are only in the breast cancer cells."​ - (American Cancer Society)