Breast cancer…
2024 American Cancer Society estimates:
However, there are reasons for optimism:
Breast cancer is a heterogeneous disease consisting of several molecular subtypes, each associated with variations in treatment response and disease-specific outcomes. Current treatment guidelines support the use of molecular analysis to identify these molecular subtypes for use in risk stratification and treatment planning. Decision-making for individual patients must consider several factors, such as tumor morphology, grade classification, tumor size, presence of lymph-node metastases, and expression of receptors (eg, estrogen, progesterone, and human epidermal growth factor receptor 2 [HER2]). At this time we know there are several subtypes of breast cancer, each with their own characteristics.2,3
Others classify subtypes based on hormone receptor (HR) and HER2 positivity or negativity (see the Understanding HR+/HER2− Breast Cancer page on this website).
Most types of breast cancer arise from the lobules or the ducts of the breast. In many cases the tumor may infiltrate the skin or components of the chest wall such as the pectoralis muscles. Tumor cells also are able to convert their microenvironment into a tumor-friendly state to promote their own growth and expansion.4,5
During normal breast development, mammary stem cells (MaSCs) are controlled by a variety of signaling pathways. These include estrogen receptors (ERs), HER2, and Wnt/β-catenin signaling pathways, which together control stem cell proliferation, cell death, cell differentiation, and cell motility.4,6 Along with having a great importance in the development and replenishment of mammary glands, MaSCs have implications in the cellular origin of breast cancer stem cells (BCSCs), which has been traced by various methods using human and mice samples. A diagram of the interplay between MaSCs and breast cancer stem cells is shown in Figure 1.4,5
Roughly 5% to 10% of breast cancers are linked to gene mutations inherited from a parent, the most common causes of which are an inherited mutation in the BRCA1 or BRCA2 genes. Women with a BRCA1 mutation have a 55% to 65% lifetime risk of developing breast cancer while those with a BRCA2 mutation have a lifetime risk of 45%.4,6Â
As a result genetic factors are a risk factor for the development of breast cancer. While the pathophysiology of breast cancer isn’t fully understood, risk factors have been identified. Certain risk factors for breast cancer are beyond an individual’s control, such as simply being a woman, as the disease is about 100 times more likely to occur in women than in men. Aging is another risk factor that inevitably increases one’s risk of breast cancer (most breast cancers are diagnosed in women age 55 years and older). A woman’s risk of developing breast cancer nearly doubles if she has a first-degree relative (mother, sister, or daughter) with breast cancer. Indeed, roughly 15% of US women who suffer from breast cancer have a family member who has been diagnosed.4,7
