What is breast cancer?

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Breast cancer is a general term for different types of cancer that develop from breast tissue cells. When abnormal cells divide in an uncontrolled manner they can form a mass of extra tissue, or tumor, which can be benign or malignant. Benign tumor cells do not spread to other parts of the body, can usually be removed and do not recur. Malignant (cancerous) tumor cells can invade nearby tissues and break away from the primary tumor to form secondary tumors (metastases) elsewhere in the body. The breast and lymph nodes: The breast contains 15 to 20 sections, or lobes. Each lobe has many smaller lobules or glands. Ducts transport milk from the glands to the nipple. Stroma (fatty tissue and ligaments) surrounds the ducts and lobules. The breast is supplied with blood and lymph vessels. Lymph vessels carry tissue fluid, or lymph, which contains immune system cells. Lymph vessels lead to small glands called lymph nodes (collections of immune system cells). Lymph node clusters draining from the breast occur under the arm, above the collarbone, in the chest and elsewhere in the body. Most cancers begin in ducts or lobules; occasionally, tumors form in non-glandular tissue. Breast tissue fluid drains into underarm lymph nodes, which filter lymph and may form a barrier against cancer cells. Cancer cells may spread to the lymph nodes or may spread around the body to other organs via the blood system. Usually, the lymph nodes are affected first; thereafter the organs most likely to be affected are the lungs, liver, bone and brain. Once the cancer has spread to the auxiliary (underarm) lymph nodes, it is more likely to have spread in the blood stream to other organs than a cancer that is just in the breast. Types of breast cancer: Breast cancer is also categorized as invasive (infiltrating) or non-invasive (in situ). Invasive cancer can grow directly into other parts of the body, or travel in blood or lymph. Non-invasive cancers may become invasive and usually do not spread, unless they have an invasive component. Invasive cancers may exist with non-invasive cancers. The cancer can be localized or multifocal. Occasionally, more than one primary tumor may be present at the same time. These are some of the more common types of breast cancer: * Infiltrating/Invasive Ductal Carcinoma (IDC) comprises 65-85% of cases. It begins in milk duct cells and can break through duct walls to invade fatty tissue. It can metastasize (spread) via blood or lymph. On a mammogram it is usually revealed as an irregular mass, micro calcifications or both. It may appear as a lump, which usually feels harder than a benign lump. * Infiltrating/Invasive Lobular Carcinoma (ILC) accounts for 5-10% of cases. It originates in milk-producing lobes, and can spread to fatty tissue and elsewhere in the body. On a mammogram, it may appear similar to IDC, but physical examination does not usually reveal a hard mass – rather a vague thickening of tissue. It can occur in more than one place in the breast (multicentric/multifocal) or in both breasts simultaneously (bilateral). * Three slow-growing invasive subtypes are Medullary, Mucinous and Tubular Carcinomas, together representing about 12% of cases. They have a better prognosis than other more common invasive cancers. * Inflammatory Carcinoma is an IDC subtype. Typically the breast becomes red, swollen and warm, and the skin thickens and may develop small bumps. This is due to rapid cancerous growth which blocks lymph vessels. In 90% of cases cancer has spread to the lymph nodes at diagnosis. Prognosis is poor: this cancer is aggressive and difficult to treat. It accounts for 1-4% of cases. * Paget's disease starts in milk ducts and can spread to the nipple and areola, causing crusting and scaling. There is usually a history of nipple inflammation or discomfort. It may be associated with in-situ or infiltrating carcinoma. If no lump can be felt, and a biopsy shows no invasive cancer, prognosis is good. The treatment is similar to invasive cancers. * Soft Tissue Tumors: Tumors may originate in the supportive tissue of the breast. These tumors are uncommon and tend to have a good outcome. As more women have regular mammograms, doctors are detecting more "non-invasive" or pre-cancerous conditions before they become full-blown cancers. They include the following: * Ductal Carcinoma In Situ (DCIS), the most common non-invasive type, occurs when cancer cells fill ducts but haven't yet spread through the walls into fatty tissue. Most women diagnosed at this stage can be cured. Without treatment, 25% of cases lead to invasive cancer within 10 years. Therefore, DCIS is treated as if it were cancer – with mastectomy or lumpectomy (removal of the tumor and a surrounding rim of normal tissue), followed by radiation to destroy any remaining malignant cells. * Lobular Carcinoma In Situ (LCIS) has no symptoms or characteristic mammography pattern. It usually occurs in multiple sites in the same breast. The risk of developing invasive cancer with LCIS is approximately one percent per year, with an equal chance of it occurring in either breast regardless of which breast had LCIS initially. LCIS is less common and less threatening than DCIS. It develops in milk-producing lobes and, when treated, does not penetrate lobule walls. LCIS does not usually become invasive itself, but may increase the risk of developing invasive cancer. For every 1 000 women with LCIS, 7.2 develop cancer within 30 years. Women with LCIS should have a mammogram and two or three physical exams each year.