Breast Cancer 101: What is Breast Cancer?

When I was diagnosed with breast cancer, I knew almost nothing about it. For all of the pink ribbons out there, all of the breast cancer awareness to be spread, I don’t think I was alone in having a fairly poor understanding of this disease. The biggest component to breast cancer awareness is breast cancer education, so I’m going to talk a bit about the basics of breast cancer.

Let’s start with some statistics:
Approximately 1 in 8 women will develop breast cancer in her lifetime.
In 2017, there were over 252,000 new cases of invasive breast cancer diagnosed.
When breast cancer is detected early, there s a 99% 5-year survival rate.

Now, what exactly is breast cancer?
Breast cancer starts with a mutation in breast cell DNA that causes the cells to grow and divide into new cells. Unlike normal cells, that grow and divide in a fairly orderly way, cancer cells grow and divide in a much more haphazard manner. These cell DNA mutations can be either inherited or happen at random. The most common inherited gene mutations are the BRCA 1 and BRCA 2 genetic mutations, but these are believed to only be responsible for less than 10% of all breast cancers. Most of the causes of environmental mutations are still unknown. When mutating cells continue to grow, they form tumors in the breast tissue, which is then identified as breast cancer.

What types of breast cancer are there?
The most common type of breast cancer is Invasive Ductal Carcinoma, breast cancer that starts in the milk ducts. This type accounts for about 80% of all breast cancer diagnoses. Less common types of breast cancer are Invasive Lobular Carcinoma, and inflammatory breast cancer. Invasive Lobular Carcinoma means that the cancer started in the milk-carrying lobules, rather than the milk ducts themselves. It accounts for approximately 10% of all breast cancers. Inflammatory breast cancer is a very rare type of breast cancer  that is characterized by reddening and swelling of the breast, rather than a distinct tumor. It accounts for only 1% of breast cancer cases. There is also a non-invasive type of breast cancer called Ductal Carcinoma In Situ (DCIS). DCIS is breast cancer that has not spread beyond the milk ducts into the surrounding tissue. It runs the risk of spreading and  eventually becoming breast cancer at a later point, but DCIS itself is considered a non-invasive cancer. Lobular Carcinoma In Situ (LCIS) can also occur, but is less common than DCIS. Breast cancer can also occur in men, but it is very rare, only accounting for about 1% of diagnoses. In addition, there are other rarely occurring types of breast cancer that can occur in other breast tissues or the nipple tissue.

Breast cancer is also categorized by the hormone receptor status of the tumor. Breast cancers can be hormone-receptor positive, which means that the tumor is fed by either estrogen receptors (ER+), progesterone receptors (PR+), or both, by the presence of receptors on the tumor that pick up these hormones. In addition, the tumor can be HER2+, which stands for Human Epidermal Growth Factor Receptor 2. HER2 gene amplification causes an overproduction of HER2 proteins in the breast tissue, causing uncontrolled division and cell growth. HER2+ breast cancers tend to be more aggressive than ER+ or PR+ breast cancers. Breast cancer can also be “triple-negative” which means that the tumor carries no hormone receptors for either estrogen or progesterone, and also does not oversimplify the HER2 gene. This type of breast cancer can be difficult to treat

What are the different stages of breast cancer?
The stages of breast cancer range from Stage 0 to Stage 4, and identifies how advanced, or widespread the cancer is through out the breast, lymph nodes, and body.
Stage 0 indicates that the cancer has not invaded outside breast tissue, and remains in the original ductal or lobular structure.
Stage 1 indicates that that the tumor in the breast is smaller than 2 millimeters and has not spread outside the breast, or that there is no breast tumor but there is a lymph node tumor smaller than 2 millimeters.
Stage 2 indicates that the tumor is smaller than 50 millimeters (5 cm) and may or may not have spread to the underarm (axillary) lymph nodes, may be present only in the lymph nodes, or may be larger than 50 millimeters and not present in the lymph nodes.
Stage 3 indicates that the tumor is of any size and has spread to the underarm lymph nodes, other lymph nodes in the breast region, and may have spread to the chest wall or the breast skin.
Stage 4 indicates that the cancer has spread (metastasized) to other parts of the body. This means that, in addition to the likely presence of a breast tumor or tumors, the cancer has spread to the area lymph nodes and into another physical system as well. The common sites for breast cancer metastasis include the bones, liver, lungs, and brain. There is not a stage beyond stage 4.

American Cancer Society
The Susan G. Komen Breast Cancer Foundation 

3 thoughts on “Breast Cancer 101: What is Breast Cancer?

  1. Emily,
    This is a fantastic resource for other women going through breast cancer. Thank you for sharing your journey with us. Although we just met, I am proud to have met you and to get to know you!
    Keep it up!


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