Breast tissue is composed of many different types of cells including adipocytes (aka: fat cells), myoepithelial cells (cells that contract to allow milk to move towards the nipple), duct cells (the cells that line the duct system), and lobular cells (cells that produce and secrete milk). Breast cancer is divided into different types depending on which of the above cells it arises from.
By far the most common type of breast cancer is "ductal carcinoma". It arises from the cells that line the milk ducts. A precursor to ductal cancer is "ductal carcinoma in situ". In this condition, the duct cells have features of cancer, but they have not yet "broken" through the tissue layer (aka: basement membrane) that separates them from the other tissue types of the breast. Cancer can also arise from the lobular cells. When this occurs it is referred to as "lobular carcinoma".
Hereditary breast cancer occurs in less than 10% of cases and is most notably caused by mutations in either the BRCA-1 or BRCA-2 genes located on chromosomes 17 and 13, respectively. The protein products of these genes normally function as "tumor suppressors" by preventing the abnormal replication of cells. However, when these genes become mutated they are no longer able to suppress abnormal replication and cancer can develop.
The known risk factors for breast cancer include: mutations in BRCA-1 or 2, nulliparity, first pregnancy at age 35 or older, menstruation beginning before age 13, menopause occurring after age 55, history of cancer, female sex (males can develop breast cancer too!), age greater than 65, and two or more first degree relatives with breast cancer.
If a breast biopsy is done that shows any of the following under the microscope, the risk of subsequently developing breast cancer is also increased: papilloma of the breast, ductal carcinoma in situ, lobular carcinoma in situ, sclerosing adenosis, and atypical hyperplasia.
Suprisingly, 70 to 75% of women who develop breast cancer have no known risk factors!
The most common presenting sign of breast cancer is a mass. Besides this, many patients will not necessarily have other symptoms unless they are late in the course of the disease. Nipple discharge (usually on the affected side only), swelling of the breast, retraction of the nipple, rashes (specifically, "peau d'orange" or an orange peel appearance), and dimpling of the breast tissue may occur.
Diagnosis of breast cancer can only be made by obtaining tissue from a suspicious area, and looking at it under the microscope. Suspicious lesions may be felt on physical exam, or seen on mammogram or ultrasound.
Tissue is most commonly obtained by fine needle aspiration or core biopsy. "Open biopsy", in which an incision is made in the breast, is sometimes also performed to obtain a specimen for further analysis.
Like other cancers, treatment is dictated by the stage of the disease. There are four stages of breast cancer based on the size of the primary tumor, whether or not lymph nodes are involved, and whether or not the cancer has spread to other organs (ie: metastatic disease).
Earlier stages of the disease (stage I and II) can sometimes be treated with lumpectomy (ie: removal of the tumor only), dissection of the axillary lymph nodes, and post-operative radiation. Later stages of the disease is usually treated with a modified radical mastectomy, which also includes lymph node dissection.
The use of chemotherapy is dependent on whether or not lymph nodes, or other organs show evidence of cancerous spread. Adjuvent therapies like tamoxifen are based on whether or not the breast cancer is positive for estrogen receptors. If it is positive for estrogen receptors then tamoxifen is given. It is a medication that binds to the estrogen receptors in breast tissue and inhibits the actions of estrogen on the breast. Unfortunately, tamoxifen acts as a stimulator of estrogen receptors in the uterus, which can increase the risk of subsequent endometrial cancer.
Breast cancer most commonly arises from the cells that line the milk ducts (ductal carcinoma). There are numerous known risk factors, although most women who develop the disease do not have any of them. Symptoms and signs include a palpable breast mass, nipple retraction, swelling of the breast, nipple discharge, and breast rashes. Diagnosis is made by taking a sample of the mass via needle aspiration or incisional biopsy and looking at it under the microscope. Treatment options depend on the stage of the disease and whether or not the breast cancer has estrogen receptors.
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