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An Overview of Cancer

Riya Singla - 11/15/2025

What is cancer?

We’ve all probably heard of cancer, but what exactly is it? Cancer is a group of diseases that is caused when the body’s cells become cancerous and begin growing and dividing at an abnormal rate. These cells spread throughout the body and may cause tumors (lumps of tissue).

 

However, not all tumors are cancerous. Benign tumors, while still painful and possibly dangerous, do not pose the same risk as cancerous/malignant tumors or spread. They are still caused by abnormal cell growth.


 

The Development of Cancer

Cancer is a genetic disease, meaning that it is caused by a change in our genes. Genetic changes can occur due to:

  • An error during cell division

  • Damage/changes to our DNA caused by harmful substances (eg. tobacco smoke and UV rays from the sun)

  • They were inherited from our parents


 

The Spread of Cancer

As the cancerous cells continue to grow in number, they begin spreading to other parts of the body through our blood vessels and lymphatic system. This process is called metastasis. From here, most types of cancers begin to form new tumors. However, some types of cancer cells (e.g. leukemia and lymphoma) don’t develop tumors, instead multiplying within the blood or lymphatic system.

 

While cancers can spread throughout all parts of the body, they are still classified based on where they first began to develop, which is called the primary cancer site. 

 

Through the blood vessels, the cells move until they get stuck somewhere, which is often a capillary. Then the cells move through the capillary walls and into the tissue of an organ that is close by. If the tissue has the nutrients it needs and meets the necessary conditions for growth, the cancer will begin to multiply and form a new tumor. Out of thousands of cancer cells, only a few survive this process.

 

Through the lymph vessels, the cells can travel to nearby lymph nodes, which are primarily located in the armpit, neck, and groin. There, some cancer cells survive and create additional tumors.



 

Types of Cancer

There are over a hundred types of cancer. They are classified by the type of tissue they originated in and the primary site. There are 6 main categories:

  • Carcinoma: Found in epithelial tissue that covers and protects organs (eg. skin) and is the most common type, accounting for 80-90% of cases.

  • Sarcoma: Originates in connective tissue, including bones, muscles, and fat.

  • Leukemia: Occurs in the bone marrow, negatively affecting red and white blood cells by producing too many not-fully-developed cells.  Unlike most cancers, leukemia does not create any tumors.

  • Myeloma: Begins in the plasma cells of bone marrow, which produce antibodies to fight infection. It’s also called multiple myeloma.

  • Lymphoma: Starts in the lymphocytes, white blood cells that are a part of the lymphatic system.

  • Mixed: The cancer begins in more than one tissue type.

 

Doctors have two staging systems to categorize how much the cancer has spread and the chance of survival:

  • TNM: The TNM system stands for Tumor, (Lymph) Node, and Metastasis

  • Numerical: Has stages 0, 1, 2, 3, and 4, with 0 being the least deadly and 4 being the most deadly.

  • Sometimes, doctors further organize the severity of the cancer using letters A, B, and C.


 

Prevention

Cancer is one of the leading causes of death across the world. Millions of people get diagnosed with cancer per year, and while mortality rates have dropped severely in recent years, hundreds of thousands still die due to the disease. While many people are at higher risk automatically due to their family history and genetics, leading a healthy lifestyle is also extremely important.

Some things you can do to achieve this are:

  • Have a nutritious diet with variety

  • Drink plenty of water

  • Don’t smoke

  • Exercise

    •  At least 150 minutes a week for adults

    • 60 minutes per day for most days for kids ages 6-17

 

Sources: 

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