Science Fair Project Encyclopedia
Breast cancer is cancer of breast tissue. Worldwide, it is the most common form of cancer in females, affecting approximately 10% of all women at some stage of their life in the Western world. Although significant efforts are made to achieve early detection and effective treatment, about 20% of all women with breast cancer will die from the disease, and it is the second most common cause of cancer deaths in women.
The risk of getting breast cancer increases with age. For a woman who lives to the age of 90 the odds of getting breast cancer her entire lifetime is about 12.5% or 1 in 8. Men can also develop breast cancer, although their risk is less than 1 in 1000 (see sex and illness). This risk is modified by many different factors. In some families, there is a strong inherited familial risk of breast cancer. Some racial groups have a higher risk of developing breast cancer - notably, women of European and African descent have been noted to have a higher rate of breast cancer than women of Asian origin. (figures from breastcancer.org)
Other established risk factors include having no children, delaying first childbirth, not breastfeeding, early menarche (the first menstrual period), late menopause and taking hormone replacement therapy.
The probability of breast cancer rises with age but breast cancer tends to be more aggressive when it occurs in younger women. One type of breast cancer that is especially aggressive and disproportionately occurs in younger women is Inflammatory Breast Cancer. It is initially Staged as Stage IIIb or Stage IV. It also is unique because it often does not present with a lump so that it often is not detected by mammography or ultrasound. It presents with the signs and symptoms of a breast infection like mastitis.
Two genes, BRCA1 and BRCA2, have been linked to the familial form of breast cancer. Women in families expressing mutations in these genes have a much higher risk of developing breast cancer than women who do not. Together with Li-Fraumeni syndrome (p53 mutations), these genetic abberations determine around 5% of all breast cancer cases, suggesting that the remainer is sporadic. Genetic counseling and genetic testing should be considered for families who may carry a heritidary form of cancer.
Due to the high incidence of breast cancer among older women, screening is now recommended in many countries. Screening methods suggested include breast self-examination and mammography. Only mammography has been proven to reduce mortality from breast cancer. In some countries routine (annual) mammography of older women is encouraged as a screening method to diagnose early breast cancer.
At this stage mammography is still the modality of choice for screening of early breast cancer. It is the gold-standard for other imaging methods such as ultrasound, MRI and CT which are less useful due to their lower spatial resolution. CT by itself is nearly useless for breast cancer screening as MRI provides better resolution and quality (and costs much more).
The U.S. National Cancer Institute recommends screening mammography with a baseline mammogram at age 35, mammograms every two years beginning at age 40, and then annual mammograms beginning at age 50. Women with a family history of breast cancer should start screening mammography at an earlier age, and it is usually suggested to start screening at an age that is 10 years less than the age at which a relative was diagnosed with breast cancer.
Breast cancers detected by mammography are usually smaller than those detected clinically, and women who undergo mammography are more likely to be eligible for breast-conserving therapy.
Many breast cancers are diagnosed now by mammography before they are large enough to be palpated, but despite screening efforts, many women are diagnosed with breast cancer after they notice a lump or when experiencing symptoms due to metastatic disease.
Breast cancer can be suspected after a cautious clinical history , physical examination and imaging (either mammography or ultrasound). The diagnosis can only be established when a suspicious lump is biopsied for histological confirmation of whether it is malignant or not. The biopsy is usually performed either with a fine needle guided by ultrasound or with a larger "core" needle. Some cases require an open biopsy after wire localization under x-ray.
A pathology report will usually contain a description of cell type and grade. Other useful information derived from the pathology laboratory include estrogen receptor and progesterone receptors status and HER2Neu status; these can help to guide treatment. The most common invasive breast cancer cell type is infiltrating ductal carcinoma . Other types include ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS), infiltrating lobular carcinoma , medullary carcinoma.
After diagnosis, the next phase is tumour staging - this aims to assess the extent of the tumour and whether or not it has metastasized (spread to distant sites).
For suspicious, high risk cases, other investigations which include CT scans, nuclear medicine imaging, chest X-rays and blood tests will be done to look for any metastasis or secondary cancer that has spread a long way from the site of the primary tumour.
The standard way of categorising tumour is by staging it using the TNM (Tumour, Nodes and Metastasis) system, which in turn determines treatment recommendations. The TNM system is specific for each type of cancer. Some biological features of the cancer such as estrogen receptor and HER2-neu oncogene expression are also determined as they also affect treatment recommendations.
The TNM classification of breast cancer:
- Tumor size:
- T0 no primary tumor found
- Tis in situ
- T1 =< 2 cm
- T1mic ≤ 0.1 cm (microinvasive)
- T1a > 0.1 to 0.5 cm
- T1b > 0.5 to 1 cm
- T1c > 1 to 2 cm
- T2 > 2 to 5 cm
- T3 > 5 cm
- T4 Chest wall /skin
- T4a Chest wall
- T4b Skin oedema (peau d'orange), ulceration, or satellite skin modules
- T4c Both 4a and 4b
- T4d Inflammatory carcinoma
- Lymph nodes:
- N0 No lymph nodes
- N1 Movable axillary
- N2a Fixed axillary
- N2b Internal mammary clinically apparent
- N3a Infraclavicular
- N3b Internal mammary clinically apparent with axillary lymph node involvement
- N3c Supraclavicular lymph nodes
- Distant metastasis:
- M0 No
- M1 Yes
- Stage 0: Tis
- Stage I: T1,N0,M0
- Stage IIA: T0-1,N1,M0 or T2,N0,M0
- Stage IIB: T2,N1,M0 or T3,N0,M0
- Stage IIIA: T3,N1,M0 or T0-3,N2,M0
- Stage IIIB: T4,any N,M0
- Stage IIIC: any T,N3,M0
- Stage IV: any T,any N,M1
The cancer is staged depending on factors which include the size of the tumour, whether there is lymph node involvement or not and whether there is distant spread of cancer cells. Stages are a composite of the TNM. Stage I is small tumor (T1) without any spread, while stage IV is metastatic disease. Stages correllate with long-term prognosis, and treatment decisions are often made on the basis of the stage.
Depending on the staging and type of the tumour, just a lumpectomy (removal of the lump only) may be all that is necessary or removal of larger amounts of breast tissue may be necessary. Surgical removal of the entire breast is called mastectomy.
Standard practice requires that the surgeon must establish that the tissue removed in the operation has margins clear of cancer, indicating that the cancer has been completely excised. If the tissue removed does not have clear margins, then further operations to remove more tissue may be necessary. This may sometimes require removal of part of the pectoralis major muscle which is the main muscle of the anterior chest wall.
During the operation, the lymph nodes in the axilla are also considered for removal. In the past, large axillary operations took out 10-40 nodes to establish whether cancer had spread - this had the unfortunate side effect of frequently causing lymphedema of the arm on the same side as the removal of this many lymph nodes affected lymphatic drainage. More recently the technique of sentinel lymph node dissection has become popular as it requires the removal of far fewer lymph nodes, resulting in fewer side effects.
At present, the treatment recommendations follow a pattern. This pattern may be adapted as every two years a worldwide conference takes place in St. Gallen, Switzerland to discuss the actual results of worldwide multi-center studies. Depending an clinical criteria (age, type of cancer, size, metastasis) patients are roughly divided to high risk and low risk cases which follow different rules for therapy. The following list is a compilation af possibilities:
- after a breast preserving therapy (lumpectomy, quadrant-resection), the high local recurrence risk (~40%) is reduced by radiation therapy to the breast
- if the lymph nodes are positive, the high mortality risk (30-80%) is reduced by systemic treatment (either anti-hormones or chemotherapy).
- in young patients, the most useful systemic therapy is chemotherapy (usually regimens such as CMF , FAC, AC and/or taxol)
- in older patients, the most useful systemic therapy is anti-hormone therapy (tamoxifen, GnRH-analogues)
- chemotherapy has increasing side effects as the patient's age passes 65
- in patients with estrogen receptor negative tumours, the most useful systemic therapy is chemotherapy
- in patients with estrogen receptor positive tumours, the most useful systemic therapy is hormone therapy
For some early tumours, systemic treatments may not be recommended if the tumor is hormone receptor negative. Radiation therapy is recommended in all patients who had lumpectomy, however radiation therapy after mastectomy is recommended only if four or more lymph nodes are involved with cancer. Radiation therapy is usually not indicated in patients with advanced (stage IV disease) except for palliation of symptoms like bone pain.
The emotional impact of cancer diagnosis, symtoms, treatment, and related issues can be severe. Most larger hospitals are associated with cancer support groups which can help patients cope with the many issues that come up in a supportive environment with other people with experience with similar issues.
On-line cancer support groups are also very beneficial to cancer patients, especially in dealing with uncertainty and body-image problems inherent in cancer treatment.
There are several prognostic factors associated with breast cancer. Stage is the single most important prognostic factor in breast cancer, as it will take into consideration local involvement, lymphnode status and whether metastatic disease is present or not. The higher the stage at the time of diagnosis, the worse the prognosis of breast cancer is. Node negative breast cancer patients have a much better prognosis compared to node positive patients.
Presence of estrogen and progesterone receptors in the cancer cell is another important prognostic factor, and may guide treatment. Hormone receptor positive breast cancer is usually associated with much better prognosis compared to hormone negative breast cancer.
Her2/Neu status has also been described as a prognostic factor. Patients whose cancer cells are positive for Her2/Neu have more aggressive disease.
Breast cancer awareness
In the month of October, breast cancer is recognized by survivors, family and friends of survivors and/or victims of the disease. A pink ribbon is worn to recognize the struggle that men and women face when battling the cancer.
- Detailed Guide: Breast Cancer
- Breast cancer
- Inflammatory Breast Cancer
- Y-ME National Breast Cancer Organization
- The Breast Cancer Site
- Breast cancer incidence by country
- National Cancer Institute - Breast Cancer Home Page
- Breast Cancer Forums with doctors answering questions
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