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What is Cancer? Introduction, Types, Stages, Treatment

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Health is “a condition of total physical, mental, and social well-being and not only the absence of disease or disability,” according to the World Health Organization. Over time, several definitions have been employed for various objectives. Healthy behaviors can be encouraged, such as regular exercise and getting enough sleep, while unhealthy behaviors, such as smoking or high levels of stress, can be reduced or avoided. Some factors that affect health are caused by personal decisions, such as whether to engage in a high-risk habit, while others are the result of structural factors, such as how society is structured and how easy or difficult it is for individuals to get essential healthcare services. Others, including hereditary illnesses, are independent of individual and community preferences.


Cancer cell


Cancer is a condition when a few of the body’s cells grow out of control and spread to other bodily regions. Since the human body contains billions of cells, cancer can develop practically everywhere. Human cells often divide (via a process known as cell growth and multiplication) to create new cells as the body requires them. New cells replace old ones when they die as a result of aging or damage. Occasionally, this systematic process fails, causing damaged or aberrant cells to proliferate when they shouldn’t. Tumors, which are tissue masses, can develop from these cells. Tumors may or may not be malignant (benign). Cancerous tumors can move to distant parts of the body to produce new tumors, invade neighboring tissues, or both (a process called metastasis). Malignant tumors are another name for cancerous tumors. Malignancies of the blood, including leukemias, seldom develop solid tumors although many other cancers do. Noncancerous tumors do not penetrate or spread to neighboring tissues. Benign tumors typically don’t come back after removal, however malignant tumors can. However, benign tumors can occasionally grow to be quite enormous. Some, like benign brain tumors, can have grave side effects or even be fatal.

How Does Cancer Develop?

Since genes that determine how our cells behave, particularly how they grow and divide, are altered, cancer is a genetic disease.

Cancer-causing genetic alterations can occur because:

  • Of mistakes that happen when cells divide.
  • Of DNA deterioration brought on by unfavorable environmental elements like the chemicals in tobacco smoke and the sun’s ultraviolet rays. (More details can be found in our section on cancer causes and prevention.)
  • They were handed down to us by our parents.

Cells with damaged DNA are typically eliminated by the body before they develop into cancer. But as we become older, the body becomes less capable of doing so. This contributes to the increased chance of developing cancer later in life.

The genetic mutations in every person’s cancer are different from one another. Additional alterations will take place as the malignancy develops further. Different cells in the same tumor may have different genetic alterations.

Properties of Cancerous cells

  • Cancer cells exhibit poorly differentiated growth and division patterns, aberrant membranes, cytoskeletal proteins, and shape. There may be a gradual change from normal cells to benign tumors to malignant tumors when the abnormalities in cells progress.
  • Self-sufficiency in growth signals: Through the activation of oncogenes like ras or myc, cancer cells develop an independent drive to proliferate—pathological mitosis.
  • Insensitivity to growth-inhibitory (antigrowth) signals: Tumor suppressor genes, such as Rb, which usually block growth, are inactivated in cancer cells.
  • Evasion of apoptosis (programmed cell death): Cancer cells silence and deactivate the genes and processes that typically allow cells to die.
  • Cancer cells have an unlimited capacity for reproduction because they activate particular gene pathways that make them immortal even after many generations of growth.
  • Tumor angiogenesis is the process through which cancer cells develop the ability to produce their own blood and blood vessels.
  • Tissue invasion and metastasis: Cancer cells develop the ability to spread throughout the body by migrating to other organs, invading other tissues, and colonizing these organs.

Causes of Cancer

The DNA in your cells has undergone mutations, which are the main cause of cancer. DNA mutations may be inherited. In addition, environmental factors may cause them to develop later in life.

These external elements, also referred to as carcinogens, may include:

  1. Physical carcinogens include radiation and ultraviolet (UV) light.
  2. Alcohol, asbestos, tobacco smoke, air pollution, poisoned food, and water are examples of chemical carcinogens.
  3. Biological cancer-causing substances such as parasites, viruses, and bacteria

Types of Genes that Cause Cancer

Proto-oncogenes, tumor suppressor genes, and DNA repair genes are the three primary gene groups that are typically impacted by the genetic alterations that cause cancer. These modifications are commonly referred to as cancer’s “drivers.”

Normal cell development and division are regulated by proto-oncogenes. However, these genes may develop into cancer-causing genes (or oncogenes), allowing cells to grow and survive when they shouldn’t by being changed in specific ways or being more active than usual.

Cell development and division are also regulated by tumor suppressor genes. Certain tumor suppressor gene mutations can cause cells to divide uncontrollably.

DNA damage must be repaired using DNA repair genes. It is common for cells with mutations in these genes to also have mutations in other genes and chromosomal abnormalities including duplications and deletions of chromosomal segments. These alterations might work together to turn the cells malignant.

Scientists have discovered that specific mutations frequently occur in a variety of cancer forms as they learn more about the molecular alterations that cause cancer. There are numerous cancer medicines on the market right now that focus on cancer-related gene alterations. No matter where cancer first developed, several of these treatments are available to anyone with a tumor that carries the targeted mutation.

When Cancer Spreads

Metastatic cancer is a type of cancer that has progressed from the site of its initial formation to another location in the body. Metastasis is the process through which cancer cells spread to other areas of the body.

The initial or original cancer’s name and cancer cell type also apply to metastatic cancer. For instance, breast cancer that spreads to the lung and develops a tumor is considered metastatic breast cancer rather than lung cancer.

Metastatic cancer cells typically resemble the original tumor’s cells when viewed under a microscope. Additionally, there are some biological similarities between metastatic cancer cells and the initial cancer cells, such as the presence of particular chromosome alterations.

Patients with metastatic cancer may occasionally live longer thanks to treatment. In other circumstances, preventing the spread of the cancer or reducing the symptoms it is causing are the main objectives of treatment for metastatic cancer. The majority of cancer patients who pass away do so through metastatic disease, which can seriously impair how the body works.

Stage of Cancer

To ascertain the degree and seriousness of your cancer, your healthcare professional will run tests. Your diagnosis will then be given a number. The greater the population, the greater the spread of the disease. Four phases are typical for malignancies. The size and location of the tumor are two of the many variables that affect the stage:

  • Stage I: Cancer has not spread to lymph nodes or other tissues; it is contained in a restricted location.
  • Stage II: Despite expanding, cancer has not yet spread.
  • Stage III: Cancer has intensified and can have migrated to the lymph nodes or other tissues.
  • Stage IV: Cancer has intensified and can have migrated to the lymph nodes or other tissues.

There is stage zero in addition to the more typical phases I through IV. Cancer in this initial stage is still contained in the region where it first appeared. Most healthcare professionals regard cancers that are still in stage zero to be pre-cancerous and are typically easily curable.

Types of Cancer

Typically, cancer types are called for the organs or tissues in which they first appear. For instance, brain cancer begins in the brain, and lung cancer begins in the lung. The type of cell that gave rise to cancer, such as an epithelial cell or a squamous cell, can also be used to describe the condition.


The most typical form of cancer is melanoma. Epithelial cells, which are the cells that line the interior and exterior surfaces of the body, are responsible for their formation. Epithelial cells come in a variety of varieties, and when examined under a microscope, they frequently resemble columns. There are distinct names for cancers that start in several types of epithelial cells:

  • Epithelial cells that create fluids or mucus are where adenocarcinoma, a type of cancer, develops. Occasionally, glandular tissues are referred to as epithelial tissues. Adenocarcinomas make up the majority of cases of breast, colon, and prostate cancer.
  • The basal (base) layer of the epidermis, which is a person’s outer layer of skin, is where basal cell carcinoma, a type of cancer, first appears.
  • Squamous cells, which are epithelial cells found just below the skin’s surface, are where squamous cell carcinoma develops. The stomach, intestines, lungs, bladder, and kidneys are just a few of the numerous organs that are lined with squamous cells. When seen under a microscope, squamous cells have a flat appearance similar to fish scales. Epidermoid carcinomas are another name for squamous cell carcinomas.
  • The epithelial tissue is known as the transitional epithelium, or urothelium where transitional cell carcinoma, a type of cancer, develops. The linings of the bladder, ureters, renal pelvis and a few other organs are made up of this tissue, which is composed of numerous layers of ectoderm cells that can develop bigger and smaller. Transitional cell carcinomas include malignancies of the bladder, ureters, and kidneys.


  • Sarcomas are tumors that develop in the muscle, fat, blood vessels, lymphatic vessels, and fibrous tissue that make up soft tissues and bone (such as tendons and ligaments).
  • The most typical type of bone cancer is osteosarcoma. Liposarcoma, Kaposi sarcoma, malignant fibrous histiocytoma, liposarcoma, and dermatofibrosarcoma protuberans are the most prevalent varieties of soft tissue sarcoma.


  • Leukemias are cancers that start in the bone marrow, which produces blood. Solid tumors are not produced by these malignancies. Instead, the bone marrow and blood become overpopulated with aberrant white blood cells (leukemia cells and leukemic blast cells), which drive out healthy blood cells. It may be more difficult for the body to manage to bleed, fight infections, or deliver oxygen to its tissues when the normal blood cell count is low.
  • There are four common forms of leukemia, which are categorized according to the type of blood cell the malignancy first appears in and if the condition worsens quickly (acute or chronic) (lymphoblastic or myeloid). Leukemia grows more swiftly in its acute forms than in its chronic variants.


  • Cancer that starts in lymphocytes is called lymphoma (T cells or B cells). These white blood cells, which are a component of the immune system, combat disease. In lymphoma, aberrant cells accumulate in the body’s lymph nodes, lymph arteries, and other organs.
  • Lymphoma comes in two primary varieties:
  • Reed-Sternberg cells, which are aberrant lymphocytes, are present in people with Hodgkin lymphoma. Usually, B cells are the source of these cells.
  • Non-Hodgkin lymphoma is a broad category of malignancies that originate in lymphocytes. The malignancies can develop from either B or T cells and can spread swiftly or slowly.

Multiple Myeloma

Plasma cells, another type of immune cell, are where multiple myeloma develops. Myeloma cells, which are aberrant plasma cells, amass in the bone marrow and develop into tumors in bones all throughout the body. Kahler disease and plasma cell myeloma are other names for multiple myeloma.


Melanocytes, which are specialized cells that produce melanin, are where melanomas, a type of cancer, first appear (the pigment that gives skin its color). The majority of melanomas develop on the skin, but they can also develop in other pigmented tissues, such as the eye.

Brain and Spinal Cord Tumors

Tumors of the brain and spinal cord can take many distinct forms. These tumors are given names based on the cell type in which they originated and the region of the central nervous system where the tumor first appeared. For instance, astrocytes, which assist maintain the health of nerve cells in the brain, are the origin of an astrocytic tumor. Malignant or benign brain tumors are also possible (cancer).

 Treatments for Cancer

  1. Chemotherapy: Chemotherapy, one of the most popular cancer therapies, uses powerful chemicals to kill cancer cells. Chemotherapy can be administered intravenously or as pills.
  2. Radiation therapy: High radiation doses are used in this treatment to eradicate cancer cells. In rare cases, radiation and chemotherapy may be administered concurrently.
  3. Hormone therapy: In some cases, hormones can inhibit other hormones that cause cancer. For instance, hormone therapy may be used to prevent prostate cancer in males whose testosterone levels are high.
  4. Biological response modifier therapy: Your immune system is stimulated by this treatment, which improves its functionality. It alters your body’s normal systems to do this.
  5. Immunotherapy: Immunotherapy, also known as biological therapy, uses the immune system of your body to treat disease. While leaving healthy cells unharmed, it can target cancer cells.
  6. Bone marrow transplant: This procedure, also known as stem cell transplantation, swaps out unhealthy stem cells for damaged ones. You will receive chemotherapy prior to the transplant to get your body ready for it.

Conceptual Question

Question 1: Who gets cancer?


Although the risk increases with age, anyone can develop cancer. Your personal risk is influenced by things including whether you smoke, your eating and exercise habits, your family’s history of cancer, and environmental and workplace variables.

Question 2: How does cancer start?


There are various types of cells in your body. Normal cellular processes include growth, division, aging, and death. The majority of the time, fresh cells then take their place. But occasionally, instead of degenerating, cells mutate, expand out of control, and form a mass or tumor.

Both benign and malignant tumors are possible (cancerous). Tissues in your body can be attacked by and killed by cancerous tumors. They may also spread to other areas of the body, where they may prompt the growth of new tumors. This procedure, known as metastasis, indicates that cancer has progressed to a late stage.

Question 3: Is cancer genetic?


In actuality, cancer is a hereditary disorder. This is due to the fact that cancer is brought on by mutations or alterations to the genes that regulate how our cells behave, resulting in abnormal cell behaviour. These gene modifications are considerably more likely to occur during a person’s lifespan due to other factors besides genetics, although they can be inherited, as they are in roughly 5–10% of all cancer cases.

Genetic testing is frequently advised when there is a known family history of hereditary cancer.

Question 4: Is there a vaccine for cancer?


There isn’t a cancer vaccine. However, there are vaccines available for some viruses known to cause cancer, including hepatitis B and the human papillomavirus (HPV).

The varieties of HPV that can result in the cervical, anal, throat, and penile cancers, as well as several other forms of cancer, can be prevented by receiving an anti-HPV vaccination. Numerous virus strains that can cause these tumors are protected by the HPV vaccine.

The same is true for hepatitis B virus infection, which has been connected to liver cancer. The hepatitis B vaccine can lower your risk of developing liver cancer. Hepatitis B vaccination, however, offers no defence against liver cancer itself, exactly like the HPV vaccine. Only the virus that might cause liver cancer is protected.

Question 5: How do cancer drugs work?


  • Chemotherapy employs drugs to eradicate cancer cells. However, the negative effects of chemotherapy can also destroy healthy cells.
  • Targeted pharmaceuticals are more recent medications that obstruct the genes or proteins found in cancer cells. Even though targeted therapy often doesn’t kill healthy cells as much, it still has adverse effects.
  • Immunotherapy treats cancer by using hormones and other medications that cooperate with your immune system.

Question 6: Does cancer have symptoms?


Occasionally, but not always. Cancer symptoms and indicators vary depending on the location and size of the tumor.

An expanding malignancy may press against adjacent organs and other structures. Signs and symptoms may be brought on by the ensuing pressure.

Some cancers develop in locations where they won’t show any symptoms until they have progressed. For instance, pancreatic cancer typically doesn’t show any indications or symptoms until it is large enough to push on nearby structures, resulting in pain, or until it starts to show symptoms of jaundice, which is characterized by skin yellowing.

Some general signs and symptoms of cancer can include:

  1. Unexplained weight loss
  2. Fever
  3. Fatigue
  4. Pain
  5. Skin changes
  6. Bowel habit or bladder function changes
  7. Sores that don’t heal
  8. Unusual bleeding or discharge

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Last Updated : 04 Jul, 2022
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