What Is Cancer?
Cancer refers to cells that grow out-of-control and invade other tissues. Cells may become cancerous due to the accumulation of defects, or mutations, in their DNA. Certain inherited genetic defects (for example, BRCA1 and BRCA2 mutations) and infections can increase the risk of cancer. Environmental factors (for example, air pollution) and poor lifestyle choices—such as smoking and heavy alcohol use—can also damage DNA and lead to cancer.Most of the time, cells are able to detect and repair DNA damage. If a cell is severely damaged and cannot repair itself, it usually undergoes so-called programmed cell death or apoptosis. Cancer occurs when damaged cells grow, divide, and spread abnormally instead of self-destructing as they should.
Malignant Tumors Vs. Benign Tumors
A tumor is an abnormal mass of cells. Tumors can either be benign (non-cancerous) or malignant (cancerous).
Benign tumors grow locally and do not spread. As a result, benign tumors are not considered cancer. They can still be dangerous, especially if they press against vital organs like the brain.
Malignant tumors have the ability to spread and invade other tissues. This process, known as metastasis, is a key feature of cancer. There are many different types of malignancy based on where a cancer tumor originates.
Metastasis is the process whereby cancer cells break free from a malignant tumor and travel to and invade other tissues in the body. Cancer cells metastasize to other sites via the lymphatic system and the bloodstream. Cancer cells from the original—or primary—tumor can travel to other sites such as the lungs, bones, liver, brain, and other areas. These metastatic tumors are “secondary cancers” because they arise from the primary tumor.
What Causes Cancer?
Certain genes control the life cycle—the growth, function, division, and death—of a cell. When these genes are damaged, the balance between normal cell growth and death is lost. Cancer cells are caused by DNA damage and out-of-control cell growth. The following is a partial list of factors known to damage DNA and increase the risk of cancer:
Some microbes are known to increase cancer risks. These include bacteria like H. pylori, which causes stomach ulcers and has been linked to gastric cancer. Viral infections (including Epstein-Barr, HPV, and hepatitis B and C) have also been linked to cancer.
Cancer may be caused by environmental exposure. Sunlight can cause cancer through ultraviolet radiation. So can air pollutants like soot, wood dust, asbestos, and arsenic, to name just a few.
Lifestyle and Diet Causes
Lifestyle choices can lead to cancer as well. Eating a poor diet, inactivity, obesity, heavy alcohol use, tobacco use including smoking, and exposure to chemicals and toxins are all associated with greater cancer risk.
Genetic mutations may cause cancer. For example, mutations of genes BRCA1 and BRCA2 (linked to an increased risk of breast and ovarian cancers) can inhibit the body’s ability to safe-guard and repair DNA. Copies of these mutated genes can be passed on genetically to future generations, leading to a genetically-inherited increased risk of cancer.
Cancer symptoms and signs depend on the size and location of the cancer as well as the presence or absence of metastasis.Every cancer and every individual is unique.
common Symptoms of cancer may include:
- Skin changes (redness, sores that won’t heal, jaundice, darkening)
- Unintended weight loss or weight gain
Other more obvious signs of cancer may include:
- Lumps or tumors (mass)
- Difficulty swallowing
- Changes or difficulties with bowel or bladder function
- Persistent cough or hoarseness
- Short of breath
- Chest pain
- Unexplained bleeding or discharge
Medical treatment with chemotherapy, radiation, targeted treatments (drugs designed to target a specific type of cancer cell) or immunosuppressive drugs used to decrease the spread of cancer throughout the body can also cause damage to healthy cells. Some “second cancers”, completely separate from the initial cancer, have been known to occur following aggressive cancer treatments; however, researchers are producing drugs that cause less damage to healthy cells (for example, targeted therapy).