Overview Of Cancer
Cancer begins in the cells, which are the building blocks of the body. Normally, the body forms new cells as you need them, replacing old cells that die. Sometimes this process goes wrong. New cells grow even when you don’t need them, and old cells don’t die when they should. These extra cells can form a mass called a tumor. Tumors can be benign or malignant. Benign tumors aren’t cancer while malignant ones are. Cells from malignant tumors can invade nearby tissues. They can also break away and spread to other parts of the body.
Cancer is not just one disease but many diseases. There are more than 100 different types. Most are named for where they start. For example, lung cancer starts in the lung and breast cancer starts in the breast. The spread of cancer from one part of the body to another is called metastasis. Symptoms and treatment depend on the type and how advanced it is. Most treatment plans may include surgery, radiation, and/or chemotherapy. Some may involve hormone therapy, immunotherapy, or other types of biologic therapy, or stem cell transplantation.
Causes Of Cancer
How Cancer Arises
Cancer is caused by certain changes to genes, the basic physical units of inheritance. Genes are arranged in long strands of tightly packed DNA called chromosomes. It is a genetic disease—that is, it is caused by changes to genes that control the way our cells function, especially how they grow and divide.
Genetic changes that cause cancer can be inherited from our parents. They can also arise during a person’s lifetime as a result of errors that occur as cells divide or because of damage to DNA caused by certain environmental exposures. Cancer-causing environmental exposures include substances, such as the chemicals in tobacco smoke, and radiation, such as ultraviolet rays from the sun.
Each person’s disease has a unique combination of genetic changes. As tumors continue to grow, additional changes will occur. Even within the same tumor, different cells may have different genetic changes.
In general, cancerous cells have more genetic changes, such as mutations in DNA, than normal cells. Some of these changes may have nothing to do with the cancer; they may be the result of it, rather than its cause.
“Drivers” of Cancer
The genetic changes that contribute tend to affect three main types of genes—proto-oncogenes, tumor suppressor genes, and DNA repair genes. These changes are sometimes called “drivers” of cancer.
Proto-oncogenes are involved in normal cell growth and division. However, when these genes are altered in certain ways or are more active than normal, they may become cancer-causing genes (or oncogenes), allowing cells to grow and survive when they should not.
Tumor suppressor genes are also involved in controlling cell growth and division. Cells with certain alterations in tumor suppressor genes may divide in an uncontrolled manner.
DNA repair genes are involved in fixing damaged DNA. Cells with mutations in these genes tend to develop additional mutations in other genes. Together, these mutations may cause the cells to become cancerous.
As scientists have learned more about the molecular changes that lead to cancer, they have found that certain mutations commonly occur in many types. Because of this, they are sometimes characterized by the types of genetic alterations that are believed to be driving them, not just by where they develop in the body and how the cancerous cells look under the microscope.
Symptoms Of Cancer
Cancer can cause many symptoms, but these symptoms are most often caused by illness, injury, benign tumors, or other problems. If you have symptoms that do not get better after a few weeks, see the doctor so that problems can be diagnosed and treated as early as possible. Often, cancer does not cause pain, so do not wait to feel pain before seeing a doctor.
Some of the symptoms that cancer may cause include:
- Breast changes
- A lump or firm feeling in the breast or under the arm
- Nipple changes or discharge
- Skin that is itchy, red, scaly, dimpled, or puckered
- Bladder changes
- Trouble urinating
- Pain when urinating
- Blood in the urine
- Bleeding or bruising, for no known reason
- Bowel changes
- Blood in the stools
- Changes in bowel habits
- Cough or hoarseness that does not go away
- Eating problems
- Pain after eating (heartburn or indigestion that doesn’t go away)
- Trouble swallowing
- Belly pain
- Nausea and vomiting
- Appetite changes
- Fatigue that is severe and lasts
- Fever or night sweats for no known reason
- Mouth changes
- A white or red patch on the tongue or in the mouth
- Bleeding, pain, or numbness in the lip or mouth
- Neurological problems
- Vision changes
- Hearing changes
- Drooping of the face
- Skin changes
- A flesh-colored lump that bleeds or turns scaly
- A new mole or a change in an existing mole
- A sore that does not heal
- Jaundice (yellowing of the skin and whites of the eyes)
- Swelling or lumps anywhere such as in the neck, underarm, stomach, and groin
- Weight gain or weight loss for no known reason
Treatment is based on the type and stage of cancer. In some people, diagnosis and treatment may occur at the same time if the tumor is entirely surgically removed when the surgeon removes the tissue for biopsy.
Although patients may receive a unique sequenced treatment, or protocol, most treatments have one or more of the following components: surgery, chemotherapy, radiation therapy, or combination treatments (a combination of two or all three treatments).
Patients with cancers that cannot be cured (completely removed) by surgery will usually get combination therapy, the composition determined by the type and stage.
Palliative therapy (medical care or treatment used to reduce disease symptoms but unable to cure the patient) utilizes the same treatments described above. It is done with the intent to extend and improve the quality of life of terminally ill patients. There are many other palliative treatments to reduce symptoms, such as pain medications and anti-nausea medications.
Types Of Oncologists
Oncology is the study of cancer. An oncologist is a doctor who treats and provides medical care for a person diagnosed with the disease.
The patient is treated by a team of health professionals who work together to plan the treatment. This team is called a multidisciplinary team (MDT).
Depending on the type and treatments, patients may be seen by some or all of these healthcare professionals:
Surgeon – a doctor who specializes in a specific cancer type and does operations.
Medical oncologist – a doctor who specializes in treatment with chemotherapy and other drugs.
Clinical oncologist – a doctor who specializes in treatment with radiotherapy, chemotherapy, and other drugs.
Hematologist – a doctor who specializes in diagnosing and treating blood disorders.
Pathologist – a doctor who studies cells and body tissues.
Clinical nurse specialist – an expert nurse who specializes in a particular area of health.
Radiologist – a specialist in x-rays and scans.
Doctors classify cancer by:
- its location in the body
- the tissues that it forms in
For example, sarcomas develop in bones or soft tissues, while carcinomas form in cells that cover internal or external surfaces in the body. Basal cell carcinomas develop in the skin, while adenocarcinomas can form in the breast.
When cancerous cells spread to other parts of the body, the medical term for this is metastasis.
A person can also have more than one type of cancer at a time.
When Cancer Spreads
In metastasis, cancerous cells break away from where they first formed (primary cancer), travel through the blood or lymph system, and form new tumors (metastatic tumors) in other parts of the body. The metastatic tumor is the same type of cancer as the primary tumor.
Cancer that has spread from the place where it first started to another place in the body is called metastatic cancer. The process by which cancerous cells spread to other parts of the body is called metastasis.
Metastatic cancer has the same name and the same type of cancerous cells as the original, or primary, cancer. For example, breast cancer that spreads to and forms a metastatic tumor in the lung is metastatic breast cancer, not lung cancer.
Under a microscope, metastatic cancer cells generally look the same as cells of the original disease. Moreover, both metastatic and original cancer cells usually have some molecular features in common, such as the presence of specific chromosome changes.
Treatment may help prolong the lives of some people with metastatic cancer. In general, though, the primary goal of treatments is to control the growth of cancerous cells or to relieve symptoms. Metastatic tumors can cause severe damage to how the body functions and most people who die of cancer die of metastatic disease.
Tissue Changes That Are Not Cancer
Not every change in the body’s tissues is cancer. However, some tissue changes may develop into cancer if they are not treated. Here are some examples of tissue changes that are not cancerous, but are often monitored:
Hyperplasia occurs when cells within a tissue divide faster than normal and extra cells build-up or proliferate. However, the cells and the way the tissue is organized look normal under a microscope. Hyperplasia can be caused by several factors or conditions, including chronic irritation.
Dysplasia is a more serious condition than hyperplasia. In dysplasia, there is also a buildup of extra cells. But the cells look abnormal and there are changes in how the tissue is organized. In general, the more abnormal the cells and tissue look, the greater the chance that cancer will form.
Some types of dysplasia may need to be monitored or treated. An example of dysplasia is an abnormal mole (called a dysplastic nevus) that forms on the skin. A dysplastic nevus can turn into melanoma, although most do not.
An even more serious condition is carcinoma in situ. Although it is sometimes called cancer, carcinoma in situ is not cancer because the abnormal cells do not spread beyond the original tissue. That is, they do not invade nearby tissue the way that cancerous cells do. But, because some carcinomas in situ may become cancerous, they are usually treated.
Types Of Cancer
There are more than 100 types of cancer. They are usually named for the organs or tissues where they form. For example, lung cancer starts in cells of the lung, and brain cancer starts in cells of the brain. Cancers also may be described by the type of cell that formed them, such as an epithelial cell or a squamous cell.