Cancer Basics
What is cancer?
- All living things - ourselves included - are made up of cells. Cells are microscopic packages of living material and we have billions of them. They come in many different types: liver cells, brain cells, blood cells and so on. In the normal adult, cells only grow and divide slowly and under very tight control to make sure that the number of cells in each tissue stays the same. Cancer begins when one cells changes and starts growing and dividing rapidly and out of control. This one cells divides to give two cells, then four, eight and so on until they form growing mass of cancer cells - called a tumour.
- In some tumours, the cells stay in the same place and as the tumour stops growing before it gets very large - often because it simply runs out space to grow. These are called benign tumours and they are not normally dangerous. We all have benign tumours, such as moles and warts. However, in other tumours the cells are able to invade the surrounding tissue and spread into nearby organs where they can cause serious and, eventually, fatal damage. These are called malignant tumours.
What do malignant and benign mean?
What is metastasis?
- In many malignant tumours, as the cells spread, they come across blood vessels. If they actually spread into the blood vessel, they get carried around the body and eventually get stuck in a smaller blood vessel in another part of the body. Here they begin to divide and grow again eventually forming a new tumour. These are called secondary tumours or metastases. This process of cancers spreading around the body is called metastasis.
Do genes cause cancer?
- Every cell carries a set of coded instructions for every activity or function that it can perform. Different genes are active in different cells, which is why a brain cell carries out many different activities from muscle cell. Genes also carry the coded instructions for basic functions of the cell such as the way cells grow and divide. The growth and division of normal cells is tightly controlled by the activity of certain genes. However, when these genes are faulty or when they mechanisms controlling the activity of these genes is damaged, it can cause the growth and division of the cells to go out of control - in other words, the become cancerous. Genes themselves do not cause cancer. When they function normally, genes prevent cancer. However, it is when some genes become damaged that they can malfunction and cause cancer.
Can you inherit cancer?
- Cancer itself cannot be inherited, but some people do inherit a higher risk of getting cancer. This is because they inherit, from their parents, a slightly damaged version of one of the genes involved in controlling cell division. On its own, this damaged gene is not enough to make cells cancerous. Normally, two or three different genes have to be damaged before a cell will become cancerous. That is why so very few of the billions of cells in our body ever become cancerous. However, if someone starts out with every cell in their body carrying damage in one of these genes, the chance of a cell getting the other types of gene damage and becoming cancerous is much higher. Some of these inherited damaged genes have been identified, such as BRCA1 and BRCA2 which increase the risk of getting breast cancer by five to seven times.
Do tumours need a blood supply?
- A tumour usually starts with a single cancerous cell that begins growing and dividing. The resulting mass of cancer cells soon gets large enough to need a new blood supply to provide oxygen and nutrients and to remove waste products. Without a blood supply, the cells in the middle of the tumour will die off. In fact, tumours without a blood supply are unable to grow more that about one millimetre across. As soon as they start growing, tumours release small, hormone-like molecules that cause nearby blood vessels to start growing towards the tumour until they actually form a new branch supplying the tumour with blood.
Understanding Breast Cancer
In this section, you can learn about how breast cancer develops, how many people get breast cancer, and what factors can increase risk for getting breast cancer. You also can learn more about signs and symptoms to watch for and how to manage any fears you may have about breast cancer.
What Is Breast Cancer?
Breast cancer is an uncontrolled growth of breast cells. To better understand breast cancer, it helps to understand how any cancer can develop.
Cancer occurs as a result of mutations, or abnormal changes, in the genes responsible for regulating the growth of cells and keeping them healthy. The genes are in each cell’s nucleus, which acts as the “control room” of each cell. Normally, the cells in our bodies replace themselves through an orderly process of cell growth: healthy new cells take over as old ones die out. But over time, mutations can “turn on” certain genes and “turn off” others in a cell. That changed cell gains the ability to keep dividing without control or order, producing more cells just like it and forming a tumor.
A tumor can be benign (not dangerous to health) or malignant (has the potential to be dangerous). Benign tumors are not considered cancerous: their cells are close to normal in appearance, they grow slowly, and they do not invade nearby tissues or spread to other parts of the body. Malignant tumors are cancerous. Left unchecked, malignant cells eventually can spread beyond the original tumor to other parts of the body.
The term “breast cancer” refers to a malignant tumor that has developed from cells in the breast. Usually breast cancer either begins in the cells of the lobules, which are the milk-producing glands, or the ducts, the passages that drain milk from the lobules to the nipple. Less commonly, breast cancer can begin in the stromal tissues, which include the fatty and fibrous connective tissues of the breast.
Over time, cancer cells can invade nearby healthy breast tissue and make their way into the underarm lymph nodes, small organs that filter out foreign substances in the body. If cancer cells get into the lymph nodes, they then have a pathway into other parts of the body. The breast cancer’s stage refers to how far the cancer cells have spread beyond the original tumor (seeStages of Breast Cancer tablefor more information).
Breast cancer is always caused by a genetic abnormality (a “mistake” in the genetic material). However, only 5-10% of cancers are due to an abnormality inherited from your mother or father. About 90% of breast cancers are due to genetic abnormalities that happen as a result of the aging process and the “wear and tear” of life in general.
While there are steps every person can take to help the body stay as healthy as possible (such as eating a balanced diet, not smoking, limiting alcohol, and exercising regularly), breast cancer is never anyone's fault. Feeling guilty, or telling yourself that breast cancer happened because of something you or anyone else did, is not productive.
Stages of Breast Cancer
| Stage | Definition |
|---|---|
| Stage 0 | Cancer cells remain inside the breast duct, without invasion into normal adjacent breast tissue. |
| Stage I | Cancer is 2 centimeters or less and is confined to the breast (lymph nodes are clear). |
| Stage IIA | No tumor can be found in the breast, but cancer cells are found in the axillary lymph nodes (the lymph nodes under the arm) OR the tumor measures 2 centimeters or smaller and has spread to the axillary lymph nodes OR the tumor is larger than 2 but no larger than 5 centimeters and has not spread to the axillary lymph nodes. |
| Stage IIB | The tumor is larger than 2 but no larger than 5 centimeters and has spread to the axillary lymph nodes OR the tumor is larger than 5 centimeters but has not spread to the axillary lymph nodes. |
| Stage IIIA | No tumor is found in the breast. Cancer is found in axillary lymph nodes that are sticking together or to other structures, or cancer may be found in lymph nodes near the breastbone OR the tumor is any size. Cancer has spread to the axillary lymph nodes, which are sticking together or to other structures, or cancer may be found in lymph nodes near the breastbone. |
| Stage IIIB | The tumor may be any size and has spread to the chest wall and/or skin of the breast AND may have spread to axillary lymph nodes that are clumped together or sticking to other structures, or cancer may have spread to lymph nodes near the breastbone. Inflammatory breast cancer is considered at least stage IIIB. |
| Stage IIIC | There may either be no sign of cancer in the breast or a tumor may be any size and may have spread to the chest wall and/or the skin of the breast AND the cancer has spread to lymph nodes either above or below the collarbone AND the cancer may have spread to axillary lymph nodes or to lymph nodes near the breastbone. |
| Stage IV | The cancer has spread — or metastasized — to other parts of the body. |
Symptoms of Breast Cancer
Initially, breast cancer may not cause any symptoms. A lump may be too small for you to feel or to cause any unusual changes you can notice on your own. Often, an abnormal area turns up on a screening mammogram (x-ray of the breast), which leads to further testing.
In some cases, however, the first sign of breast cancer is a new lump or mass in the breast that you or your doctor can feel. A lump that is painless, hard, and has uneven edges is more likely to be cancer. But sometimes cancers can be tender, soft, and rounded. So it's important to have anything unusual checked by your doctor.
According to the American Cancer Society, any of the following unusual changes in the breast can be a symptom of breast cancer:
- swelling of all or part of the breast
- skin irritation or dimpling
- breast pain
- nipple pain or the nipple turning inward
- redness, scaliness, or thickening of the nipple or breast skin
- a nipple discharge other than breast milk
- a lump in the underarm area
These changes also can be signs of less serious conditions that are not cancerous, such as an infection or a cyst. It’s important to get any breast changes checked out promptly by a doctor.
Breast Cancer Risk and Risk Factors
By now you may be familiar with the statistic that says 1 in 8 women will develop invasive breast cancer. Many people misinterpret this to mean that, on any given day, they and the women they know have a 1-in-8 risk of developing the disease. That’s simply not true.
In reality, about 1 in 8 women in the United States — 12%, or about 12 out of every 100 — can expect to develop breast cancer over the course of an entire lifetime. In the U.S., an average lifetime is about 80 years. So, it’s more accurate to say that 1 in 8 women in the U.S. who reach the age of 80 can expect to develop breast cancer. In each decade of life, the risk of getting breast cancer is actually lower than 12% for most women.
People tend to have very different ways of viewing risk. For you, a 1-in-8 lifetime risk may seem like a high likelihood of getting breast cancer. Or you may turn this around and reason that there is a 7-in-8, or 87.5%, chance you will never get breast cancer, even if you live to age 80. How you view risk often depends on your individual situation — for example, whether you or many women you know have had breast cancer, or you have reason to believe you are at higher-than-normal risk for the disease — and your usual way of looking at the world.
Even though studies have found that women have a 12% lifetime risk of developing breast cancer, your individual risk may be higher or lower than that. Individual risk is affected by many different factors, such as family history, reproductive history, lifestyle, environment, and others.
This section is designed to help you better understand breast cancer risk and some of the factors that can increase risk.
Managing Breast Cancer Fears
So many women you know may have had breast cancer — friends and neighbors, coworkers, relatives. It seems as if every time you turn around, breast cancer is being talked about in the newspaper or on TV. You may be fearful of developing breast cancer for the first time or of receiving a diagnosis after a mammogram or other testing. If you’ve had breast cancer, you may be fearful of a possible recurrence or even of the possibility that breast cancer could take your life.
Even though you may have some of these fears, you are not necessarily going to get breast cancer. If you have had breast cancer before, it doesn’t mean that the cancer will recur. Still, it's normal to have concerns about a disease that you hear about and see around you relatively often — and that you may have experienced yourself or through a loved one.
Breast Self-Exams
It was once widely recommended that women check their own breasts once a month. But studies suggest these breast self-exams play a very small role in finding cancer. The current thinking is that it's more important to know your breasts and be aware of any changes, rather than checking them on a regular schedule. If you want to do breast self-exams, be sure to go over the technique with your doctor.
Breast Ultrasound and MRI
Besides a mammogram, your doctor may order additional imaging with breast ultrasound. An ultrasound can help determine the presence of cysts, fluid-filled sacs that are not cancer. An MRI may be recommended along with a mammogram for routine screening in certain women who have a higher risk of breast cancer.
What If You Find a Lump?
First, don't panic. Eighty percent of breast lumps are not cancerous. Lumps often turn out to be harmless cysts or tissue changes related to your menstrual cycle. But you should let your doctor know right away if you find anything unusual in your breast. If it is cancer, the earlier it's found the better. And if it's not, testing can give you peace of mind.
Breast Biopsy
The only sure way to determine whether a lump is cancer is to do a biopsy. This involves taking a tissue sample for further examination in the lab, sometimes through a small needle. Sometimes surgery is done to take part of or the entire lump for testing. The results will show whether the lump is cancer, and if so, what type. There are several forms of breast cancer, and treatments are carefully matched to the type of cancer.
Hormone-Sensitive Breast Cancer
Some types of breast cancer are fueled by the hormones estrogen or progesterone. A biopsy can reveal whether a tumor has receptors for estrogen (ER-positive) and/or progesterone (PR-positive). About two out of three breast cancers are hormone sensitive. There are several medications that keep the hormones from promoting further cancer growth.
The image shows a molecular model of an estrogen receptor.
HER2-Positive Breast Cancer
In about 20% of patients, breast cancer cells have too many receptors for a protein called HER2. This type of cancer is known as HER2-positive, and it tends to spread faster than other forms of breast cancer. It's important to determine whether a tumor is HER2-positive, because there are special treatments for this form of cancer.
Breast Cancer Stages
Once breast cancer has been diagnosed, the next step is to determine how big the tumor is and how far the cancer has spread. This process is called staging. Doctors use Stages 0-4 to describe whether cancer is localized to the breast, has invaded nearby lymph nodes, or has spread to other organs, such as the lungs. Knowing the stage and type of breast cancer will help your health care team formulate a treatment strategy.
Radiation Therapy for Breast Cancer
Radiation therapy uses high-energy rays to kill cancer cells. It may be used after breast cancer surgery to wipe out any cancer cells that remain. It can also be used along with chemotherapy for treatment of cancer that has spread to other parts of the body. Side effects can include fatigue and swelling or a sunburn-like feeling in the treated area.
Hormone Therapy for Breast Cancer
Hormone therapy is an effective treatment for women with ER-positive or PR-positive breast cancer. These are cancers that grow more rapidly in response to the hormones estrogen or progesterone. Hormone therapy can block this effect. It is most often used after breast cancer surgery to help keep the cancer from coming back. It may also be used to reduce the chance of breast cancer developing in women who are at high risk.
Targeted Drugs for Breast Cancer
Targeted therapies are newer drugs that target specific properties within cancer cells. For example, women with HER2-positive breast cancer have too much of a protein called HER2. Targeted therapies can stop this protein from promoting the growth of cancer cells. These drugs are often used in combination with chemotherapy. They tend to have milder side effects compared to chemotherapy.
Life After Diagnosis
There's no doubt that cancer is a life-changing experience. The treatments can wear you out. You may have trouble managing daily chores, work, or social outings. This can lead to feelings of isolation. It's crucial to reach out to friends and family for support. They may be able to go with you to treatments, help out with chores, or just remind you that you are not alone. Many people choose to join a support group -- either locally or online.
Breast Cancer Treatment
Surgery is the mainstay of therapy for breast cancer. The choice of which type of surgery is based on a number of factors, including the size and location of the tumor, the type of tumor and the person's overall health and personal wishes. Breast-sparing surgery is often possible.
The cancer is staged, using the information from surgery and from other tests. Staging is a classification that reflects the extent and spread of a tumor and has an impact on treatment decisions and also the prognosis for recovery.
- Staging in breast cancer is based on the size of the tumor, which parts of the breast are involved, how many and which lymph nodes are affected, and whether the cancer has metastasized to another part of the body.
- Cancers may be referred to as invasive if they have spread to other tissues. Those that do not spread to other tissues are called noninvasive. Carcinoma in situ is a noninvasive cancer.
Breast cancer is staged from 0 to IV.
- Stage 0 is noninvasive breast cancer, that is, carcinoma in situ with no affected lymph nodes or metastasis. This is the most favorable stage of breast cancer.
- Stage I is breast cancer that is less than 2 cm (3/4 in) in diameter and has not spread from the breast.
- Stage II is breast cancer that is fairly small in size but has spread to lymph nodes in the armpit OR cancer that is somewhat larger but has not spread to the lymph nodes.
- Stage III is breast cancer of a larger size, greater than 5 cm (2 in), with greaterlymph node involvement, or of the inflammatory type.
- Stage IV is metastatic breast cancer: a tumor of any size or type that has metastasized to another part of the body. This is the least favorable stage.
Treatment is based on many factors, including:
- Type and stage of the cancer
- Whether the cancer is sensitive to certain hormones
- Whether the cancer overproduces (overexpresses) a gene called HER2/neu
In general, cancer treatments may include:
- Chemotherapy medicines to kill cancer cells
- Radiation therapy to destroy cancerous tissue
- Surgery to remove cancerous tissue -- a lumpectomy removes the breast lump; mastectomy removes all or part of the breast and possible nearby structures
Hormonal therapy is prescribed to women with ER-positive breast cancer to block certain hormones that fuel cancer growth.
- An example of hormonal therapy is the drug tamoxifen. This drug blocks the effects of estrogen, which can help breast cancer cells survive and grow. Most women with estrogen-sensitive breast cancer benefit from this drug.
- Another class of hormonal therapy medicines called aromatase inhibitors, such as exemestane (Aromasin), have been shown to work just as well or even better than tamoxifen in postmenopausal women with breast cancer. Aromatase inhibitors blockestrogen from being made.
Targeted therapy, also called biologic therapy, is a newer type of cancer treatment. This therapy uses special anticancer drugs that target certain changes in a cell that can lead to cancer. One such drug is trastuzumab (Herceptin). It may be used for women with HER2-positive breast cancer.
Cancer treatment may be local or systemic.
- Local treatments involve only the area of disease. Radiation and surgery are forms of local treatment.
- Systemic treatments affect the entire body. Chemotherapy is a type of systemic treatment.
Most women receive a combination of treatments. For women with stage I, II, or III breast cancer, the main goal is to treat the cancer and prevent it from returning (curing). For women with stage IV cancer, the goal is to improve symptoms and help them live longer. In most cases, stage IV breast cancer cannot be cured.
Prevention
The most important risk factors for the development of breast cancer are sex, age, andgenetics. Because women can do nothing about these risks, regular screening is recommended in order to allow early detection and thus prevent death from breast cancer.
Regular screening includes breast self-examination, clinical breast examination, and mammography.
Breast self-examination (BSE) is cheap and easy. Routine monthly examination may be helpful. Previously considered critical, more recent studies suggest that self breast exam may be less valuable than previously thought, especially for women who are having routine clinical breast examination and/or mammography.
- For women who are menstruating, the best time for examination is immediately after the monthly period.
- For women who are not menstruating or whose periods are extremely irregular, picking a certain date each month seems to work best.
- Instruction in the technique of breast self-examination can be obtained from your health-care provider or from any one of several organizations interested in breast cancer.
Clinical breast examination: The American Cancer Society recommends a breast examination by a trained health-care provider once every three years starting at age 20 years, and then yearly after age 40 years.
Mammograms are recommended every one to two years starting at age 40 years. For women at high risk for the development of breast cancer, mammogram screening may start earlier, generally 10 years prior to the age at which the youngest close relative developed breast cancer.
Obesity after menopause and excessive alcohol intake may increase the risk of breast cancer slightly. Physically active women may have a lower risk. All women are encouraged to maintain normal body weight, especially after menopause and to limit excess alcohol intake. Hormone replacement should be limited in duration if it is medically required.
In women who are genetically at high risk for the development of breast cancer, tamoxifen has been shown to significantly decrease the incidence of the disease. Side effects should be carefully discussed with your health-care provider prior to embarking on therapy. A second drug, raloxifene (Evista), which is now being used for the treatment of osteoporosis, also blocks the effects of estrogen and appears to prevent breast cancer. Initial studies showed that both tamoxifen and raloxifene were able to reduce the risk of invasive breast cancer, but raloxifene did not have this protective effect against noninvasive cancer. Studies are ongoing to further characterize the effectiveness and indications for use of raloxifene as a breast cancer preventive drug.
Occasionally, a woman at very high risk for development of breast cancer will decide to have a preventive or prophylactic mastectomy to avoid developing breast cancer. Additionally, removal of the ovaries has shown to reduce the risk of developing breast cancer in women who have the BRCA1 mutation and who have their ovaries surgically removed before they reach age 40.
There is still little agreement about whether lifestyle changes can prevent breast cancer. The best advice is to eat a well-balanced diet and avoid focusing on one "cancer-fighting" food. The American Cancer Society's dietary guidelines for cancer prevention recommend that people:
- Choose foods and portion sizes that promote a healthy weight
- Choose whole grains instead of refined grain products
- Eat 5 or more servings of fruits and vegetables each day
- Limit processed and red meat in the diet
- Limit alcohol consumption to one drink per day (women who are at high risk for breast cancer should consider not drinking alcohol at all
https://www.breastcancer.org
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