Cancer is a group of more than 100 different diseases characterized by the growth of abnormal cells that divide rapidly, uncontrollably and have the ability to invade and destroy other cells or tissues of the body. It is induced by carcinogens which are substances that cause gene mutation. Once cancer develops, then treatment is required because it cannot go on its own. Although several treatment options such as Chemotherapy, Targeted therapy, Surgery, radiotherapy, Hormone therapy, Immunotherapy, and Clinical Trials exist, none is guaranteed to cure cancer. But early diagnosis can lead to successful cure of cancer.  Cancer cells can grow anywhere in the body and because cancer is a collection of diseases,  it has varying names such as prostate cancer, breast cancer, lung cancer etc.

How does a Normal Cell Develops into a Cancer Cell?

The human body is made up of trillions of cells and each day at least 10 million of these cells die and need to be replaced. For example the cells in your skin need to be replaced after every 2 to 3 weeks. The body has therefore put in place a way (or mechanism) to control how cell grow and die naturally (programmed cell death or apoptosis). This mechanism is under instructions from genes within your DNA. Therefore, anything that interferes with these instructions will cause normal cells to behave abnormally. Abnormal cell behavior will eventually lead to cancer.

Cancer cells, therefore results from a sequential or progressive mutation overtime of essential genes that are responsible for maintaining a balance between cell growth and cell death. Because the body also fights back in trying to repair these mutations, the development of cancer (called carcinogenesis) is a slow process. It usually becomes successful when there is an accumulate damage to these genes such that the body finds it difficult to repair them anymore.

Once enough genetic damage has taken place, cells may start to divide uncontrollably or fail to die. This results to the formation of an abnormal mass of solid tissue called a tumor. A tumor can be benign (non-cancerous) or malignant (cancerous). A benign tumor is not cancer and will not spread to other parts of the body and can easily be treated. However, if left untreated, then a benign tumor can become cancerous. A malignant tumor on the other hand is cancerous and can spread to other parts of the body. Also, not all types of cancer form a solid tumor. This includes most types of cancer of the blood such as leukemia, lymphoma, and myeloma.

Cancer is hardly inherited although you can be genetically predisposed to it. Genetic predisposition means that you may have certain genetic diseases or characteristics that make you vulnerable under certain environmental conditions or lifestyle such as smoking.

sDifferences between a Cancer cell and a Normal Cell

Cancer cells and normal cells have key major differences that are usually used for their identification and to develop suitable treatments.  Cancer cell differ from normal cell in the following ways:

  • Cancer cells grow rapidly and uncontrollably compared to normal cells: For a cell to divide or grow and then stop, it needs to receive signals from the body. Normal cells receive such signals and divide or grow only when needed. Normal cells also undergo programmed cell death (apoptosis) when they are old or no longer needed  by obeying signals from the body. Cancer cells however are autonomous. They ignore such signals or instructions and cannot be regulated or controlled. Consequently, they keep dividing and growing rapidly and uncontrollably.
  • Cancer cells do not mature into specialized cells while normal cells mature into specialized and distinct cell types. Because of rapid and uncontrollable cell division, cancer cells do not have enough time or chance to mature into specialized and distinct cell types capable of carrying out a specific function. Normal cells on the other hand, mature into specialized and distinct cell types capable of carrying out a specific function. For example the cells of the liver called the hepatocytes are specialized and take part in metabolism, detoxification, or protein synthesis.
  • Cancerous cells can spread to any part of the body but normal cells are localized within their site of origin and cannot spread beyond. Normal cells secrete adhesion substances which cause them to stick together in a group or to stay in one place. Cancer cells however, may not secrete such substances. This will give them the ability to float freely or to detach from their original site. As a result, they can float to nearby tissues or be carried away by the blood stream or lymphatic system to other parts of the body.  The spread of cancer cells from their site of origin to other parts of the body is called metastasis. A cancer cell which spread to other parts of the body from its site of origin is said to have metastasized. 
  • A cancer cell is invasive, but a normal cell is not. Cancer cells may push up against and attack nearby healthy cells and tissues. An invasive cancer cell can influence nearby normal cells to develop new blood vessels. Such blood vessels keep the tumor alive by providing it with oxygen and nutrients and removing waste. This helps to sustain the cancer cell growth and to keep it alive.
  • Cancer cells trick the immune system but normal cells do not. The immune system is a complex defense system the body uses to fight and destroy anything abnormal or foreign. When a normal cell starts to behave abnormally or gets damaged, the immune system identifies and remove them. Therefore, the immune system can also be used to fight cancer. Cancer cells however trick (or evade) the immune system by secreting certain substances. Because of this, the immune system on its own cannot  get rid of cancer. 
  • A cancer cell generates its energy mainly from glycolysis while a normal cell generates only a small portion of its energy through glycolysis. Normal cells generate energy (in the form of ATP) through 3 different processes namely glycolysis, Kreb’s cycle and oxidative phosphorylation. Most of the energy is generated through oxidative phosphorylation in the presence of oxygen and very little from glycolysis. Cancer cells however generate most of their energy through glycolysis whether oxygen is present or not. It will only rely on oxidative phosphorylation if glycolysis is suppressed. 
  • Cancer cells are immortal but normal cells have a lifespan. Normal cells cannot divide forever and will eventually die. Cancer cells however have figured out a way to divide and grow continuously and forever. 
  • Cancer cells look different to normal cells when viewed under a microscope. In comparison to normal cells, the sizes of cancer cells might be smaller or larger. In addition, the shape of both the cell and nucleus is very abnormal. The nucleus of a cancer is larger and darker.

Difference between a Primary and a Secondary Tumor

Cancer can also be referred to as a tumor. A primary tumor is cancer that is still localized at its primary site (the site where it started). Cancer that has moved away from its primary site to other parts of the body is called a metastasis or a secondary tumor

Types of Cancer

There exist more than 100 different types of cancer. They can be named  based on their site of origin. For example, liver cancer originates from the liver and lung cancer originates from the lungs.  A more general description or classification is based on the type of cell or tissue structure the cancer is made up of. Based on this, the following types of cancer exist:

  • Carcinoma: Carcinomas refer to cancer of the epithelial tissues and are mostly solid tumors. Also, they are the most common types of cancer.
    Epithelial cells are cells which line both the inner and the outer surfaces of the body such as the skin and the bladder. There are different types of epithelial cells or tissues in the body. Based on this, a carcinoma can have a specific name based on the type of epithelial tissue it originated from. Adenocarcinoma is cancer which originates from epithelial cells that produce fluids or mucus. Examples of adenocarcinomas include breast, colon, and prostate cancer. 
  • Sarcoma: A Sarcoma refers to cancer of the connective tissues such as fat, bones, muscle, cartilage, blood vessels and lymph vessels. 
  • Leukemia: Leukemia is cancer of the blood which develops from the bone marrow and produces useless white blood cells unable to either fight infections or remove damaged cells. Four main types of leukemia exist and include acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, and chronic myeloid leukemia.
  • Lymphoma: Lymphoma refers to cancer of the lymphatic tissues and affects the lymphocytes (B Cells and T-cells). Lymphocytes are disease fighting white blood cells which form a complex network for fighting infections. There are 2 main types of lymphoma namely  Hodgkin lymphoma and non-Hodgkin lymphoma. Hodgkin lymphoma  mostly affects the B-cells while non-Hodgkin lymphoma can affect either the B-cells or the T-cells. 
  • Melanoma: Melanoma is cancer which affects the melanocytes. Melanocytes are cells which make melanin, the pigment responsible for the color of the skin. 
  • Cancer of the brain, spinal cord or nerves: No specific or general description exist for cancer affecting the nervous tissues (brain, nerves and spinal cord). However, they can be named based on the specific type of nervous tissue which is being affected. For example, astrocytoma is cancer affecting the astrocytes which are cells that help to support and keep the nerve cells healthy. Glioblastoma is cancer of the glial tissues. Glial cells provides physical and metabolic support to neurons. 

In addition to these, many other types of cancer such as multiple myeloma, carcinoid, endometrial  cancer etc. exist. 

 

Causes of Cancer

 The DNA within a cell is made up of genes. A gene is the basic physical and functional unit of inheritance and code for specific proteins, or segments of proteins, which have differing functions within the body. Cancer is primary caused by gene mutation within the DNA of cells. But, there is no single cause for  gene mutation. Therefore, cancer can be caused by several factors including:

  • Infectious agents such as viruses
  • Smoking
  • Exposure to chemicals
  • Exposure to radiation
  • Presence of autoimmune diseases
  • Errors in replication
  • Genetically inherited diseases
  • Genetic composition or makeup. This takes into account family history, age, gender and skin type. 

How to Prevent cancer

Cancer can be prevented in the following ways:

  • Genetic counselling. Your genetic makeup or family history can put you at risk of developing cancer. Genetic counseling will help you determine your genetic risk of having cancer and advice you on what to do.
  • Go for regular checkup and including cancer screening exams. Cancer at the early stage can easily be treated. 
  • Vaccinate against cancer causing viruses such as papillomavirus, Helicobacter pilori, hepatitis B and hepatitis C.
  • Eat properly and get a healthy diet.
  • Maintain a healthy weight. Avoid being under weight or overweight.
  • Avoid exposure to chemicals, radiation and excessive heat.
  • Stop smoking.
  • Drink alcohol only in moderation.
  • Pratice safe sex to avoid infections.
  • Get into healthy hygiene practices.
  • Exercise regularly.

Signs and Symptoms of Cancer

There are different types of cancer and they are present in different parts of the body. Each type can come with specific signs and symptoms. However, general signs and symptoms associated with all cancer types include:

  • Persistent and unexplained cough, fever or night sweats
  • Bloody urine, stool, vomit or coughing with blood
  • Difficulties swallowing
  • Feeling unease after eating
  • Observed differences in your digestion pattern
  • Difficulties breathing
  • Persistent sore throat
  • Unexplained weight loss or gain
  • Muscle and/or joint pain
  • Fatigue
  • Persistent lump (area of thickening under the skin) or soar that fails to heal.
  • Unexplained bruises or bleeding
  • Changes in your urination pattern
  • Changes in skin pigmentation such as yellowing, redness or darkening.
  • A birth mark or mole that changes in shape, size or pigmentation.

Careful observation and you will realize that these signs and symptoms are similar to that with most other diseases. It is therefore the responsibility of the individual concern to be vigilant and to quickly go for check if you suspect something is not right. 

Diagnosis of Cancer

No single test is used to diagnose cancer because some diseases or infectious agents can mimic the signs and symptoms of cancer. Effective diagnosis of cancer can be achieved with the following test:

  • Physical examination: Here, the doctor looks for changes or abnormalities on your body such as changes in skin color, lumps on the body or organ enlargement. 
  • Laboratory test: This is used to measure the level of different chemical components or substance in your body. Some common lab test used to diagnose cancer include urinalysis, blood tests, complete blood count, and measurement of tumor markers. Tumor markers are substances produced by both cancer and normal cells in response to any benign or malignant abnormality. Although made by both normal and cancer cells, the levels of tumor markers is much higher in cancer cells. An unusual number or type of white blood cell can also be used as an indicator for diagnosing certain cancers such as leukemia. 
  • Imaging tests: These tests are used by the doctor to examine your internal features or organs in a noninvasive way. It gives valuable pictures about your body structure and organs which are used to detect any abnormalities, confirm cancer and measure the extent of the disease. Imaging tests used to diagnose cancer include, CT scan, bone scan, MRI, PET scan, ultrasound, X-ray, and nuclear scan. 
  • Biopsy: A biopsy is a procedure used to extract a sample of cells or tissues from the body for examination under a microscope. A biopsy is used to evaluate whether cells are abnormal, to determine if abnormal cells are benign or malignant, to evaluate the extent of the disease and determine its cause. A biopsy is mostly performed by a surgeon and its the main method used to diagnose cancer. Under a microscope, normal cells look uniform, have similar sizes and orderly arranged. Cancer cells however, appear abnormal, have very different sizes, and are unorganized. 

Treatment of Cancer

There exist different treatment methods for curing cancer. Each treatment method comes with its own advantage and disadvantages or side effects. The 7 treatment methods available for curing cancer include Chemotherapy, Targeted therapy ( also called Molecular Targeted therapy), Surgery, radiation therapy (also called radiotherapy), Hormone therapy, Immunotherapy, and Clinical Trials. The most common methods used to treat cancer include chemotherapy, radiotherapy and surgery. 

The following treatment options are used to cure cancer:

  1. Chemotherapy: Chemotherapy uses a drug or chemical substance to target rapidly dividing cells by obstructing several processes such as DNA replication, protein folding and unfolding, obstruction of metabolic pathway etc. Chemotherapeutic drugs are not very specific towards their cancer target and usually attack normal cells as well.
  2. Targeted Therapy: Compared to chemotherapeutic drugs, targeted therapies are a class of drugs (small molecules, antibodies or a combination of both) which target specific processes or molecules involved in carcinogenesis and tumor growth. Because they are specific, more cancer cells are killed by far compared to normal cells and many of the side-effects observed with chemotherapy will be absent although severe side-effects have been observed in some cases.
  3. Surgery: Surgery is usually the first preferred option and suitable when the cancer cell is still localized at its site of origin. 
  4. Radiotherapy: Radiotherapy uses high doses of ionizing radiations to kill cancer cells completely. It can be employed as the only form of treatment, to shrink cancer cells before another treatment, to destroy any remaining cells after another treatment or in combination with other treatments such as chemotherapy, surgery or hormone therapy. Radiotherapy is a continuous treatment and will not cause cancer cells to die immediately.  Death of cancer cells occurs after days or weeks when they must have suffered sufficient damage.
  5. Hormone Therapy: Some cancer cells trick the body to secrete hormones which will be used for their own advantage. Hormone therapy therefore aims to block these hormones or stop their production or interfere with their function and by so doing cancer cell growth is slowed down or inhibited completely. 
  6. Immunotherapy: Immunotherapy  aims to restore or enhance the immune system so that they can better fight or destroy cancer cells. 
  7. Clinical Trials: All other treatment methods may fail. When this happens, clinical trials may be your last option. Your doctor will help you determine if you need clinical trials and will also help you find one. Taking part in a clinical trial is purely the patient’s choice and it might either work or not.

Cancer cannot go away on its own and treatment is required in most cases. Therefore talk to your doctor about your treatment options if you are diagnosed with cancer. 

No specific treatment is guaranteed to cure cancer, but some treatments can cure  you and not others. For some people, cancer can be cured using only one treatment type but for others a combination of more than one treatment method such as surgery with chemotherapy and/or radiotherapy is required.