• Breast Anatomy

    • The breast in a premenopausal woman is composed of glandular tissue, fat, connective tissue and ducts; the axillary tail of breast tissue is tucked upward in the axilla. The breast lies on the pectoralis muscles of the thorax.
    • The breast is divided by irregular fibrous septa which prevent masses from migrating from one area of the breast to another; malignant tumors may eventually erode through these septa.
    • Lymphatic channels travel throughout the breast, with all but the most medial portions draining to the axillary lymph nodes. The “sentinel” node—the first node to receive drainage from the breast—can be determined with testing and evaluated for metastatic spread.
    • Post-menopausal women have little glandular tissue since most of it has been replaced by fat.
  • Cancer Metastasis

    • Cancer tends to spread by two mechanisms: infiltration, in which the tumor pushes against and enters contiguous tissue; and metastasis, when cancer cells enter lymphatic channels and/or small blood vessels and eventually travel to distant locations and organs in the body.
    • Certain tumors have a predilection for specific sites. Colon cancer frequently spreads to the liver, and breast cancer to the brain and spine.
    • When there is lymphatic spread, the local and regional lymph nodes are the first line of defense; when the nodes fill up with dividing tumor cells, the cells then break free and travel toward the heart for distribution throughout the body.
  • Lead-Time Bias

    • A common assumption is that a cancer may not have been diagnosed early enough to make a difference, with the assumption being that early diagnosis is always better.
    • In reality, cancers are present for very long periods of time before they are diagnosable, and many have metastasized prior to the period in which they can be detected.
    • The life span of more than 60% of cancer patients is essentially predetermined by the characteristics of the cancer itself. While a patient diagnosed earlier may live “longer” than one diagnosed later, both patients actually survive about the same length of time from the first cancer cell.
  • Mammography

    • Mammography is an imaging technique which allows visualization of breast tissue. Fat, glandular tissue and ductal tissue have characteristic densities and patterns.
    • Solid tumors are generally easier to see in older patients with larger amounts of fat within the breasts, but can be difficult to see in patients with “dense” breasts (young women and women with fibrocystic breasts).
    • Approximately 75% of breast cancers can be seen on mammography, with the patient’s breast characteristics being the largest determining factor.


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