molecule CD24 was used to identify breast cancer stem cells. In addition, another marker for these cells is the expression of the enzyme aldehyde dehydrogenase (ALDH). Together the presence of CD44 and ALDH expression and low or absent expression of CD24 represents the most widely used identifiers for isolating breast cancer stem cells. When these cells were isolated and transplanted into immunodeficient mice, they generated tumors. However, these proteins are not the most accurate markers, and current research efforts are being directed at discovering other markers.
Arvind Suresh
Independent Scholar
See Also: Breast: Cell Types Composing the Tissue; Breast: Current Research on Isolation or Production of Therapeutic Cells; Breast: Development and Regeneration Potential.
Further Readings
Fu, Naiyang, Geoffrey J. Lindeman, and Jane E. Visvader. “The Mammary Stem Cell Hierarchy.” Current Topics in Developmental Biology, v.107 (2014).
Guo, Wenjun. “Concise Review: Breast Cancer Stem Cells: Regulatory Networks, Stem Cell Niches, and Disease Relevance.” Stem Cells Translational Medicine (2014).
Rios, Anne C., et al. “In Situ Identification of Bipotent Stem Cells in the Mammary Gland.” Nature, v.506/7488 (2014).
Roy, Somdutta, et al. “Rare Somatic Cells From Human Breast Tissue Exhibit Extensive Lineage Plasticity.” Proceedings of the U.S. National Academy of Sciences, v.110/12 (2013).
Breast Cancer
Breast Cancer
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Breast Cancer
Breast cancer is a type of cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas, while those originating from lobules are known as lobular carcinomas. Breast cancer can occur in both men and women, but most of them occur in women. Breast cancer screening harms and benefits are controversial, but it is generally started at the age of 50 years in all women. Surgery is the most effective treatment for breast cancer. Chemotherapy and hormonal therapy also play a role in treatment. Radiation is used after breast-conserving surgery to prevent relapses. Hormonal receptors play an important role in pathogenesis and the treatment of breast cancer. Estrogen receptors, progesterone receptors, and HER2/neu receptors all are known to be expressed by most types of breast cancers, and the breast cancers that do not express these receptors are called triple negative breast cancers and they show resilience to all sorts of treatments.
Breast Development and Anatomy
Human breast development is a progressive process that is initiated during embryonic life. The glandular maturation occurs at puberty, while full breast differentiation is attained only with subsequent pregnancy and lactation. Breast tissue is composed of both epithelial and stromal elements. The epithelial components are branching ducts that connect the structural and functional units of the breast (the lobules) to the nipple. The stroma, which comprises the majority of the breast volume in the nonlactating state, is composed of adipose and fibrous connective tissue. The principal blood supply of the breast is derived from the internal mammary artery. Approximately one-third of the blood supply (mainly to the upper outer quadrant) is provided by the lateral thoracic arteries. Lymph flow from the deep subcutaneous and intramammary vessels moves centrifugally toward the axillary lymph nodes.
Types of Breast Cancer
In situ breast cancer refers to cancer in which the cells have remained within their place of origin—they have not spread to breast tissue around the duct or lobule. One type of noninvasive cancer called ductal carcinoma in situ (DCIS) is considered a precancerous lesion. This means that if it were left in the body, DCIS could eventually develop into an invasive cancer. Another type of noninvasive cancer called lobular carcinoma in situ (LCIS) is not considered precancerous because it won’t eventually evolve into invasive cancer. LCIS does, however, increase the risk of cancer in both breasts.
Invasive (infiltrating) breast cancers spread outside the membrane that lines a duct or lobule, invading the surrounding tissues. The cancer cells can then travel to other parts of your body, such as the lymph nodes. The type of tissue where breast cancer arises determines how the cancer behaves and what treatments are most effective. Parts of the breast where cancer begins include:
Figure 1 Anatomy of the human female breast
Source: Medline Plus.
Milk ducts
Ductal carcinoma is the most common type of breast cancer. This type of cancer forms in the lining of a milk duct within the breast. The ducts carry breast milk from the lobules, where it is made, to the nipple.
Milk-producing lobules
Lobular carcinoma starts in the lobules of the breast, where breast milk is produced. The lobules are connected to the ducts, which carry breast milk to the nipple.
Connective tissues
Rarely breast cancer can begin in the connective tissue that is made up of muscles, fat, and blood vessels. Cancer that begins in the connective tissue is called sarcoma. Examples of sarcomas that can occur in the breast include phyllodes tumor and angiosarcoma.
Pathological Types of Breast Cancer
Cancer cells with unique appearances
When viewed under a microscope, invasive ductal carcinoma cells look different from healthy cells. Subtypes of invasive ductal carcinoma that describe how the cells appear under a microscope include tubular, mucinous, medullary, and papillary.
The degree of difference between the cancer cells and normal cells
Breast cancer cells are compared to normal cells for grading. Breast cancers are graded on a 1 to 3 scale, with grade 3 cancers being the most different looking and considered the most aggressive. Some breast cancers are sensitive to the body’s naturally occurring female hormones—estrogen and progesterone. The breast cancer cells have receptors on the outside of their walls that can catch specific hormones that circulate through the body. Knowing breast cancer is sensitive to hormones gives physicians a better idea of how best to treat the cancer or prevent cancer from recurring. Breast cancer can be divided into types on the basis of hormonal expression.
Estrogen receptor (ER) positive. This type of breast cancer is sensitive to estrogen.
Progesterone receptor (PR) positive. This type of breast cancer is sensitive to progesterone.
Hormone receptor (HR) negative. This type of cancer does not have hormone receptors, so it will not be affected by treatments aimed at blocking hormones in
