Statistics: Cancer is one of the most spread and death-causing diseases worldwide. According to NIH (National Cancer Institute, U.S.A.), more than 14 million new cases of cancer and more than 8 million cancer-related deaths are registered in 2012 worldwide. The researchers of cancer are expecting the rise of new cases` number up to 23.6 million per year by 2030.
Getting informed and prepared is one of the most efficient ways to counter cancer, that is why we answer the most important question about the disease in this article:
- What is cancer and how it appears in the body?
- What is the difference between normal and cancer cells?
- How does cancer arise and spread?
- Which types of cancer are there?
- Who is predisposed to cancer and why?
- How to prevent cancer and find it in early stages?
What is Cancer?
Actually, scientists combine a wide collection of related diseases with the term “cancer”. All types of cancer are caused by the unstoppable process of cell division and their spread into any surrounding tissues of the body.
Each human body consists of trillions of cells. These cells are programmed to grow and divide correspondingly to the needs of our bodies. The cells are constantly renewed: old and damaged cells die and newly created cells take their places. The process is balanced, although it does not tolerate any errors.
The development of cancer begins at some point, when the described process breaks or experiences damages. Old and damaged cells start to survive, and new cells start to form where and when they are not actually needed. These new cells begin to divide without control and it lead to the tumor growth.
Cancer tumors can be of 2 types: malignant and benign. Malignant tumors spread and invade to nearby tissues, while benign tumors usually do not spread across the body. Malignant tumors are considered as much more dangerous, mainly because of their ability to break off cancer cells and spread them to distant places of the body through blood and lymph systems. This process is called metastasis.
However, not all types of cancer form tumors. Solid tumors are distinctive for the types of cancer which are formed by the masses of tissue. There are also blood- and lymph-related cancer types, which do not have solid tumors.
Normal Cells Vs Cancer Cells
Cancer cells have a number of differences, which provide them with the ability to constantly grow. First of all, cancer cells have no specialization. Unlike normal cells, which are always grown by the body for a specific reason, cancer cells ignore the factor of specialization and spread without control.
Furthermore, cancer cells are able to ignore the programmed cell death signal from the body. This process is called apoptosis and is crucial for the body to get rid of the damaged or unneeded cells.
Additionally, cancer cells acquire the ability to influence the neighboring normal cells and reconstruct them for their own purposes. For instance, cancer cells can form additional blood vessels to support their viability with oxygen and nutrients and to gain the opportunity to grow even further.
It is also important, that cancer cells get the ability to evade the immune system. Normally, immune system would kill and remove damaged cells, but some of them are able to hide their presence and begin the tumor growth process.
How Cancer Arises and Spreads
Cancer is a disease caused by changes to genes. The genes control every cell from its formation to its death. Genetic changes influence the way cells grow and divide, and can run the cancer process.
The mentioned genetic changes can be caused by 2 main types of reasons: inherited from parents and obtained through lifetime (see “Risk Factors for Cancer” below to learn more about environmental exposures and lifestyle habits that can cause cancer).
Each case of cancer is unique, because each person`s genetic combination is different from others. While cancer progresses, more and more genetic changes apply to the cells.
There are essentially 3 types of genes, which tend to be influenced by cancer changes mostly:
- Proto-oncogene is normally involved in cell growth and division process, but gives the cells an opportunity to survive and grow much more than they should, when influenced by cancer alteration.
- Tumor suppressor usually control the cells` growth and division, but in its altered version allows cells to divide uncontrollably.
- DNA repair gene is called to fix damaged DNA parts, but develops even further mutations under the influence of damaged genes.
During the research of cancer scientists have mentioned certain types of genes` mutations, that cause cancer in most of the observed cases. Therefore, cancer types are now being characterized more by the genetic alteration type as by the place in the body where they have been detected.
These investigations also help to research the method, that cancer commonly uses to spread across the body. Metastatic cancer represents the stage of the disease, when damaged cells are spread from the initial growth place to another, across the body.
The most important thing about metastatic cancer is that the cells of initial tumor and the spread cells represent the identical type of mutation. These cells have comparable molecular features and the same chromosome changes.
The metastatic stage of cancer is lethal for most of the patients, because tumors have already done severe damage to the body and the spread of cancer cells can hardly be controlled.
Types of Cancer
There are lots of cancer type (more than 100) and much more are currently researched and not yet classified. As we have already mentioned, cancer types have been traditionally named by the part of the body where they appear, but this approach does not reflect the essence of the disease.
The most common cancer types can be gathered into the following categories on the basis of specific cell types they damage:
Carcinoma influences epithelial cells, which cover the inside and outside surfaces of our body.
Epithelial cells are also divided into several types, and carcinomas are categorized correspondingly:
- Adenocarcinoma affects epithelial cells that produce fluids or mucus.
- Basal cell carcinoma applies damage to the outer layer of skin.
- Squamous cell carcinoma refers to the cells right beneath the outer surface of the skin, as well as most organs` cover (lungs, stomach, kidneys, bladder).
- Transitional cell carcinoma relates to the special type of epithelium found in the linings of the ureters, bladder, and some parts of the kidneys.
Sarcoma hits bones and soft tissues like fat, muscle, blood and lymph vessels, fibrous tissue (tendons and ligaments).
Osteosarcoma relates to the most frequent case of bone cancer. Among the most common cases of the soft tissue sarcomas could be named: liposarcoma, leiomyosarcoma, malignant fibrous histiocytoma, Kaposi sarcoma, and dermatofibrosarcoma protuberans.
Leukemia starts in the blood-forming tissue of the bone marrow and spreads through blood. This type of cancer forms no solid tumors, but produces lots of abnormal white blood cells and crowds out normal blood cells. This effect causes the lack of oxygen delivered to tissues, complicates bleeding control and blocks the normal function of immune system.
Leukemia is categorized by disease flow rate to acute or chronic, and by blood cell type initially damaged to lymphoblastic or myeloid.
Lymphoma affects the disease-fighting white blood cells called lymphocytes (T cells and B cells). Lymphoma forces abnormal lymphocytes to build up nodes and lymph vessels in lymph and organs.
Lymphomas are divided into 2 types: Hodgkin lymphoma (usually forms abnormal lymphocytes from B cells) and Non-Hodgkin lymphoma (all other types of cancers related to lymphocytes).
Multiple myeloma also deals with the immune system of the body. It affects plasma cells, which are normally called to fight diseases in our body.
Myeloma cancer cells are formed from the normal plasma cells, which build up in the bone marrow. These cancer cells tend to form tumors in bones and then spreads across the body through blood and lymph.
Melanoma damages the cells of the skin, beginning with the special cell types called melanocytes. Melanocytes normally produce melanin —the skin color pigment.
Melanomas can also appear in other pigmented tissues, such as an eye.
Risk Factors for Cancer
Unfortunately, there is no fixed list of factors that could be applied to everyone. However, there are lots of research studies, which narrows the circle of risk factors for cancer. According to NIH studies (National Cancer Institute, U.S.A.), these risk factors are:
- Age — 1/4 of all new cancer cases are met within the age category between 65 and 74.
- Alcohol — alcohol drinking is scientifically confirmed as the cause of several cancer types.
- Chronic Inflammation — over a long period can cause DNA damage and lead to cancer.
- Diet — some specific dietary components or nutrients can potentially lead to cancer, but there are yet no scientific conclusion on the topic.
- Hormones — menopausal and other types of hormone therapy can increase the cancer risk rate.
- Immunosuppression — research has shown the dependence of transplantation-related medications and the increased risk of a various cancer types.
- Infectious Agents — some infectious agents, such as viruses, bacteria, and parasites, can increase the risk of forming cancer cells.
- Obesity — obese people have an increased risk of several types of cancer; moreover, a healthy diet and physical activity may be helpful in reducing the risk cancer.
- Radiation — ionizing radiation is proved to damage DNA and cause cancer.
- Sunlight — ultraviolet radiation exposure damages the skin and can lead to skin-type cancer.
- Tobacco — the leader among the causes of cancer and death from cancer.
Prevention of Cancer
Essentially, there are 3 vital steps to minimize your chances to get cancer, or at least to detect it on the very early stage an effectively cure it:
- Screening Tests. Consult with your physician on available screening methods and do not forget to repeat them at least once per year.
- Get Vaccinated. Human Papillomavirus (HPV) and Hepatitis B can cause cancer, but you can get vaccinated against this threat.
- Healthy Lifestyle. Lots of risk factors for cancer are listed above, but most of them could be easily avoided just by keeping your lifestyle healthy: eat healthy food, keep on physical activity, do not smoke, do not drink alcohol, protect yourself from sunburn etc.
Despite of all risks, cancer can be kept at a distance. The most important thing is to be informed about the disease and to be ready to fight it at the early stages, when the chances to cure are very high.
Remember, that your health is always in your hands!