Here are the sobering facts:

  • Cancer is the second leading cause of death in the United States, a very close second to heart disease. In fact, in 2011, 596,339 died from heart disease while 573,313 died from cancer1.
  • Cancer is the leading cause of death for those who are 45-74 years old.
  • After accidents, it’s the second leading cause of death for ages 1-44.
  • In our lifetime, 50% of us will develop some form of cancer.
  • 1 in 4 of us will die of cancer.

These are the somber statistics that don’t even include basal cell and squamous cell carcinomas of the skin. It means that, while heart disease is what kills most of us after we’ve lived to old age, it’s cancer that shortens our lives.

And yet, for how common cancer is, it is very misunderstood by most.

As a surgical oncologist, I’ve had to deliver many cancer diagnoses. I’ve also had to witness the effect it has on my patients too many times. Sometimes, the response is a stunned silence. Sometimes, it’s panic. Other times, it’s deflated acceptance. Many of my patients receive the diagnosis like it’s a death sentence.

Most, if not all of us, have family members or friends that have gone through cancer treatment with terrible results. I can see that those families and friends jump to the forefront of my patients’ minds.

I want my patients to understand what cancer really is, hence this series.

To understand what cancer is, we have to understand a little bit of how our bodies are built, and how they function.

Our bodies are made of trillions of cells—30 trillion, by most estimates. Each cell has a specialized role for which it’s been designed:

  • Skin cells: Provide a barrier.
  • Bone cells: Make bone that gives us support.
  • Muscle cells: Contract and allow us to move.

And so on.

Within each cell is a genome made of DNA that acts as a blueprint for how the cell is constructed and how it functions.

Changes in the genome, or the way the cell reads the genome, can lead to problems with the function of the cells. Most of the time, these damaged cells die or are destroyed by the body.

Sometimes, however, a cell divides and multiplies without any control. This is essentially what cancer is: the unregulated and uncontrolled growth of cells that can invade or spread. 

Cancer is not a single disease.

Cancer is not a monolithic entity with uniform treatments and outcomes. There is a huge variety of cancers.

Often, when you read the popular news outlets or watch the evening news, it’s easy to get the impression that medical science has cured cancer. Every few months, people are told about some kind of breakthrough in research that has cured cancer. This is confusing to patients who then visit their doctor and are told that there’s no guaranteed cure for them. It’s because the breakthrough in research is for a specific type of cancer in a specific kind of patient. The breakthrough is almost never applicable to cancer in other patients with other tumors.

So then, it’s important to understand the different kinds of cancers. A few of the major types are: carcinomas, sarcomas, leukemias, lymphomas, germinomas, and central nervous system cancers.

  • Carcinomas: The most common of cancers, it starts from epithelial cells (the cells that line our insides and outsides). Cancers of the skin, throat, lungs, and endocrine glands, breast, and prostate are usually carcinomas.
  • Sarcomas: These are tumors of mesenchymal cells. Mesenchymal cells are the cells that make up muscle, bone, fat, blood vessels, and cartilage.
  • Leukemia: These are cancers of the blood, and do not form tumors.
  • Lymphomas: Cancers of the lymphoid tissue, which are part of the immune system.

In summary, there’s a different kind of cancer for almost every type of cell and every type of tissue in our body. Their progression, their results, and their treatments are all variable, too.

  • Some cancers grow slowly, while others progress rapidly.
  • Some cancers are almost uniformly fatal, while others rarely cause death.
  • A few cancers have very focused and effective therapies that don’t cause man side effects. But most cancers use toxic chemotherapy, radiation, and surgery.

Further still, within each type of cancer is tremendous variability. For example: Just because someone is diagnosed with papillary thyroid cancer doesn’t mean that they’ll have the same outcome and process as another person diagnosed with papillary thyroid cancer. This holds true for almost every type of cancer.

Staging systems

All of that variability is a lot to deal with. That’s why “staging systems” were developed to try and figure out how severe one’s cancer is, and how aggressively to treat it.

Staging systems have two purposes:

  1. To determine prognosis—the likely outcome of the cancer, i.e. how likely it is that the cancer will be cured, come back, relapse, spread out, or cause death.
  2. To determine treatment. Higher stage cancers with a worse prognosis deserve more aggressive treatment, even if the treatment is more toxic and damaging.

Most staging systems go from stage 1 to stage 4, with 1 being the earliest and least concerning, and 4 being the most advanced and dangerous.

For solid cancers, the staging systems are generally based on the size and extent of the tumor, whether it has spread to lymph nodes nearby and whether it’s spread to other parts of the body.

Sometimes, factors such as age and gender are also used to determine the stage. More recently, genetic tests and tumor markers have been included in determining the prognosis and treatment. For leukemias, the staging is based on age, genetic testing, and laboratory studies.


Part 2 of this series on cancer, we investigate what causes cancer and how we can reduce our risk. In Part 3, Dr. Lee discusses conventional treatment methods for cancer–namely surgery, radiation therapy and chemotherapy.

1 Hoyert DL, Xu JQ. Deaths: Preliminary data for 2011. National vital statistics reports; vol 61 no 6. Hyattsville, MD: National Center for Health Statistics. 2012.


About the Author

Steve Lee, MD, PhD

Dr. Lee is a surgical oncologist and associate professor at Loma Linda University School of Medicine and currently serves as Vice Chairman of the Head and Neck Surgery Department and co-director of the Center for Skull Base Surgery. He lives in Redlands, CA with his wife and two daughters and enjoys dragging them out into the great outdoors every chance he gets.

3 comments on “Understanding Cancer, Part 1/4: What Is It?

  1. I find the Understanding Cancer series by Steve Lee, MD, Ph.D. to be very interesting, understandable, and relevant to me and my family.
    Will there be parts 3 and 4? When might they be available?

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