The colon (large intestine) serves a vital purpose in the human body. It is where the body extracts water, salt, and nutrients from solid waste. The waste then proceeds through the rectum, which escorts it out of the body by way of the anus.
Colon cancer can occur when growths, called polyps, develop on the inner lining of the large intestine. As far as cancer-related deaths go, it is the third leading cause in the United States in men and women. One in 23 men and one in 25 women will develop colon cancer in their lifetime. This insidious killer is expected to claim 53,200 lives in 2020. That’s almost 140 people per day. Many times, polyps can be removed during a routine colonoscopy before they have the opportunity to develop into cancer. This is why it is so important to undergo routine colon screenings.
How Colon Cancer Starts
Many colon cancers begin as a growth, called a polyp, on the inner lining of the colon. There are types of polyps that, over the course of many years, can develop into cancer. However, it is important to note that not all polyps will convert into cancer. The likelihood of a polyp developing into cancer is dependent on the kind of polyp it is, as there are several different types:
• Adenomas (adenomatous polyps) are polyps that sometimes develop into cancer. They are referred to as a pre-cancerous condition. There are three variations of adenomas: tubular, villous, and tubulovillous.
• Hyperplastic and Inflammatory Polyps occur more commonly and are generally not considered to be pre-cancerous. However, if a patient is discovered to have a hyperplastic polyp measuring greater that 1cm, they may need to be screened for colon cancer more frequently. This is because a polyp larger than 1cm can be more likely to contain cancer. It can also increase a patient’s chances of developing colon cancer.
• Sessile Serrated Polyps (SSP) and Traditional Serrated Adenomas (TSA) are treated as a pre-cancerous condition as they are at an increased risk of becoming colon cancer.
Additionally, if more than three polyps are present or if dysplasia (an area where cells look abnormal) can be seen in a polyp once it has been removed, there is a greater possibility that the polyp contains cancer.
How Colon Cancer Spreads
If cancer develops in a polyp, it can eventually grow into the colon’s wall, which is comprised of multiple layers. The cancer begins in the mucosa (the deepest layer) then can grow through some or all of the remaining layers.
After the cancer cells are in the wall of the colon, they are able to grow into the blood or lymph vessels. Once in these vessels, the cells are able to move anywhere in the body. This spreading of cancerous cells is call metastasis. The extent of metastasis is determined by how far down the cancer grows into the wall of the intestine and if it has spread (metastasized) outside of the colon.
Different Types of Colon Cancer
There are several types of cancer that affect the colon. The most common is called an adenocarcinoma, which makes up the majority of colon cancers at 95%. This type of cancer begins in the lining of the large intestine. Oftentimes, it starts in the inner lining and then will spread to the other layers.
There are also two less frequently-occurring subtypes of adenocarcinoma, which can be more aggressive and more complicated to diagnose and treat:
• Mucinous Adenocarcinoma This type of adenocarcinoma accounts for 10-15% of all colon adenocarcinomas. It consists of at least 50% mucus, which can cause the cancerous cells to spread more rapidly.
• Signet Ring Cell Adenocarcinoma Accounting for fewer than 1% of adenocarcinomas, the name is derived from the way it looks under a microscope. It is extremely rare and equally as difficult to treat.
There are also other types of tumors that, while far less common, can also originate in the colon. Gastrointestinal Carcinoid Tumors begin from cells in the intestine that produce hormones. While they only make up 1% of all colon cancers, they account for half of all small intestine cancers.
The following cancers are exceptionally rare and combined are responsible for fewer than 5% of all colon cancer cases:
• Lymphomas This immune system cell cancer primarily gets its start in the lymph nodes; however, it can begin in other organs, including the colon.
• Sarcomas A cancer which can originate in the muscle layers, blood vessels, or other connective tissues found in the wall of the colon.
• Gastrointestinal Stromal Tumors (GISTs) These tumors start from the interstitial cells of Cajal, which are unique cells in the wall of the colon. Some of these tumors can be benign (non-cancerous) and can be located at any point in the digestive tract. They are not commonly found in the colon.
Recognizing the Symptoms
Colon cancer may present with few to no symptoms in its early stages. Should any symptoms appear and persist, it is of utmost importance to schedule an appointment for a colon cancer screening. Early stage symptoms may include:
In the later stages of colon cancer, symptoms are more evident. A person may experience the symptoms listed above in addition to:
If the cancer has metastasized to other areas of the body, such as the lungs or liver, symptoms may also present that are associated with that area.
Stages of Colon Cancer
After a colon cancer diagnosis, a physician may refer to the cancer by “stage.” This is a way of determining how advanced the cancer is. Knowing what stage the cancer is in is imperative, as it allows the doctor to prepare the optimum treatment plan and give the patient a long-term prognosis. Stage 0 is the earliest stage of colon cancer, with stage 4 being the most advanced. The following breaks down each stage:
• Stage 0 This is also referred to as carcinoma in situ, when abnormal cells are located only in the colon’s inner lining.
• Stage 1 At this stage, the cancer has infiltrated the lining of the colon and possibly the muscle layer. It has not metastasized to other areas of the body.
• Stage 2 The cancer has extended to the walls of the colon and possibly progressed through the colon walls to tissues close by. It has not affected the lymph nodes.
• Stage 3 This is when the cancer has spread to the lymph nodes but has not yet moved to other areas of the body.
• Stage 4 The stage in which the cancer has metastasized to other organs, like the lungs and liver.
Treatment
The method that is employed to treat colon cancer will greatly depend on the type as well as the stage of the cancer. When considering a treatment plan, a physician will also take into account other factors such as the age and general health of the patient.
There is not yet a “cure” for any type of cancer, although there are a host of treatment options available. The primary goal of treatment is to remove the cancer if possible; however, it can also help slow or even prevent its spread. It can also aid in the reduction of symptoms, making the patient more comfortable. The three most commonly utilized treatments include surgery, chemotherapy, and radiation.
The Risk Factors
There are certain risk factors for the development of colon cancer that cannot be prevented and are important to share with a physician during screening:
There are also risk factors, such as lifestyle choices, that are preventable. The risk of colon cancer can be reduced by making these changes:
Getting Screened
It is highly recommended that screening begin around the age of 50 for those with an average risk of colon cancer. Those at higher risk are encouraged to begin screening sooner.
There are multiple screening options available; some can be performed from the comfort of home. It is important to discuss all of the alternatives with a physician to determine the most appropriate choice.
Disclaimer: This article is for informational purposes only and is not intended to be a substitute for professional consultation or advice related to your health or finances. No reference to an identifiable individual or company is intended as an endorsement thereof. Some or all of this article may have been generated using artificial intelligence, and it may contain certain inaccuracies or unreliable information. Readers should not rely on this article for information and should consult with professionals for personal advice.
