Cancer Definition, Types, and Causes

Cancer Definition, Types, and Causes


As an oncologist, I often find that one of the most important steps in empowering my patients is educating them about the disease they are facing. My name is Dr. Ekta Vala, and my mission is to provide clear and comprehensive information about cancer. Understanding cancer definition, types, and causes is crucial for both patients and their loved ones. This knowledge not only helps in coping with the diagnosis but also in making informed decisions about treatment and lifestyle changes. In this blog, I will delve into the cancer definition, types, and causes, shedding light on this complex disease that affects millions worldwide.

Cancer Definition

Cancer is a term used to describe a group of diseases characterized by the uncontrolled growth and spread of abnormal cells. These abnormal cells can form tumors (masses) or spread through the bloodstream and lymphatic system to other parts of the body. The process by which normal cells become cancerous involves genetic mutations that disrupt normal cell growth and division, leading to malignant (cancerous) cells that can invade and destroy healthy tissue.

Types of Cancer

Understanding the different types of cancer is essential, as each type can vary significantly in its behavior, treatment, and prognosis. The main categories include:

  1. Carcinomas:
    • Carcinomas are cancers that begin in the epithelial cells that line the skin and internal organs. They are the most common type of cancer and include breast cancer, lung cancer, and colorectal cancer.
  2. Sarcomas:
    • Sarcomas originate in the connective tissues such as bones, muscles, and fat. Examples include osteosarcoma (bone cancer) and liposarcoma (fat tissue cancer).
  3. Leukemias:
    • Leukemias are cancers of the blood and bone marrow. They involve the overproduction of abnormal white blood cells. Examples include acute lymphoblastic leukemia (ALL) and chronic myeloid leukemia (CML).
  4. Lymphomas:
    • Lymphomas are cancers of the lymphatic system, which is part of the body’s immune system. The two main types are Hodgkin lymphoma and non-Hodgkin lymphoma.
  5. Myelomas:
    • Myelomas are cancers that begin in the plasma cells of the bone marrow. Multiple myeloma is the most common type, affecting the body’s ability to produce normal blood cells.
  6. Central Nervous System Cancers:
    • These cancers start in the tissues of the brain and spinal cord. Examples include gliomas and astrocytomas.

Causes of Cancer

The causes of cancer are multifaceted, involving a combination of genetic, environmental, and lifestyle factors. Understanding these causes can help in cancer prevention and early detection. Here are some of the primary causes:

  1. Genetic Factors:
    • Genetic mutations can be inherited from parents or acquired over a lifetime. Inherited mutations, such as those in the BRCA1 and BRCA2 genes, can significantly increase the risk of breast and ovarian cancers.
  2. Environmental Factors:
    • Exposure to certain environmental elements can increase cancer risk. These include:
      • Tobacco Smoke: Smoking is a leading cause of lung cancer and is linked to several other cancers, including mouth, throat, and bladder cancer.
      • Radiation: Exposure to ultraviolet (UV) radiation from the sun can cause skin cancer, while exposure to ionizing radiation from X-rays and certain radioactive materials can increase the risk of various cancers.
      • Carcinogens: Chemicals and substances like asbestos, benzene, and certain pesticides are known carcinogens that can cause cancer.
  3. Lifestyle Factors:
    • Lifestyle choices play a significant role in cancer development. These include:
      • Diet and Nutrition: Diets high in processed foods, red meats, and sugary beverages can increase cancer risk, while diets rich in fruits, vegetables, and whole grains can help protect against cancer.
      • Physical Activity: Regular physical activity can reduce the risk of several cancers, including breast and colorectal cancer.
      • Alcohol Consumption: Excessive alcohol intake is linked to cancers of the mouth, throat, liver, and breast.
      • Obesity: Being overweight or obese increases the risk of several types of cancer, including endometrial, breast, and pancreatic cancer.
  4. Infections:
    • Certain infections can increase cancer risk. These include:
      • Human Papillomavirus (HPV): HPV infection is linked to cervical, anal, and oropharyngeal cancers.
      • Hepatitis B and C: Chronic infection with these viruses can lead to liver cancer.
      • Helicobacter pylori: Infection with this bacterium is associated with an increased risk of stomach cancer.
  5. Hormonal Factors:
    • Hormonal imbalances and exposure to certain hormones can influence cancer risk. For example, prolonged exposure to estrogen, either naturally or through hormone replacement therapy, can increase the risk of breast and endometrial cancers.
  6. Immune System Dysfunction:
    • A weakened immune system, whether due to HIV/AIDS, immunosuppressive drugs, or autoimmune diseases, can increase the risk of cancers like Kaposi sarcoma and certain lymphomas.

Cancer Prevention

Understanding cancer definition, types, and causes underscores the importance of prevention strategies. Here are some key preventive measures:

  1. Avoid Tobacco:
    • Quitting smoking and avoiding secondhand smoke are crucial steps in reducing cancer risk.
  2. Healthy Diet:
    • Adopting a diet rich in fruits, vegetables, and whole grains while limiting red meat and processed foods can help protect against cancer.
  3. Regular Exercise:
    • Engaging in regular physical activity can lower the risk of several cancers.
  4. Limit Alcohol:
    • Reducing alcohol consumption can decrease the risk of various cancers.
  5. Protect Against UV Radiation:
    • Using sunscreen, wearing protective clothing, and avoiding tanning beds can help prevent skin cancer.
  6. Vaccinations:
    • Getting vaccinated against HPV and hepatitis B can prevent cancers caused by these infections.
  7. Regular Screenings:
    • Participating in regular cancer screenings can help detect cancer early when it is most treatable. Screenings include mammograms, Pap smears, colonoscopies, and skin exams.


Understanding cancer definition, types, and causes is the first step in the fight against this complex disease. By being informed, you can take proactive measures to reduce your risk and improve your overall health. As an oncologist, I encourage you to adopt a healthy lifestyle, stay informed about your risks, and participate in regular screenings. Cancer prevention is a continuous effort that involves making informed choices and staying vigilant about your health. Together, we can work towards a future where cancer is less prevalent, and more lives are saved through early detection and prevention.