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Chapter 086. Breast Cancer (Part 1)

Harrison's Internal Medicine Chapter 86. Breast Cancer Breast Cancer: Introduction Breast cancer is a malignant proliferation of epithelial cells lining the ducts or lobules of the breast. In the year 2007, about 180,510 cases of invasive breast cancer and 40,910 deaths occurred in the United States. Epithelial malignancies of the breast are the most common cause of cancer in women (excluding skin cancer), accounting for about one-third of all cancer in women. As a result of improved treatment and earlier detection, mortality from breast cancer has begun to decrease substantially in the United States. This chapter will not consider rare. | Chapter 086. Breast Cancer Part 1 Harrison s Internal Medicine Chapter 86. Breast Cancer Breast Cancer Introduction Breast cancer is a malignant proliferation of epithelial cells lining the ducts or lobules of the breast. In the year 2007 about 180 510 cases of invasive breast cancer and 40 910 deaths occurred in the United States. Epithelial malignancies of the breast are the most common cause of cancer in women excluding skin cancer accounting for about one-third of all cancer in women. As a result of improved treatment and earlier detection mortality from breast cancer has begun to decrease substantially in the United States. This chapter will not consider rare malignancies presenting in the breast such as sarcomas and lymphomas but will focus on the epithelial cancers. Human breast cancer is a clonal disease a single transformed cell the product of a series of somatic acquired or germline mutations is eventually able to express full malignant potential. Thus breast cancer may exist for a long period as either a noninvasive disease or an invasive but nonmetastatic disease. These facts have significant clinical ramifications. Genetic Considerations Not more than 10 of human breast cancers can be linked directly to germline mutations. Several genes have been implicated in familial cases. The Li-Fraumeni syndrome is characterized by inherited mutations in the p53 tumorsuppressor gene which lead to an increased incidence of breast cancer osteogenic sarcomas and other malignancies. Inherited mutations in PTEN have also been reported in breast cancer. Another tumor-suppressor gene BRCA-1 has been identified at the chromosomal locus 17q21 this gene encodes a zinc finger protein and the product therefore may function as a transcription factor. The gene appears to be involved in gene repair. Women who inherit a mutated allele of this gene from either parent have at least a 60-80 lifetime chance of developing breast cancer and about a 33 chance of developing ovarian .