Colorectal cancer begins when healthy cells of the mucosa of the colon or rectum mutate and exit control, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, which means it can grow and spread to other parts of the body (metastasis). A benign tumor means that the tumor can grow but will not spread. These changes usually take years to occur and develop.

Genetic and environmental factors can cause these changes. However, when a person has a hereditary syndrome (see Risk Factors), changes can occur in a shorter time.

Anatomy of the Colon & Rectum

The colon and rectum form the large intestine, which plays an important role in the body’s ability to process food waste.

The colon and rectum are divided into 5 sections. The ascending colon is the portion extending from an area called cecum. The cecum is the beginning of the large intestine in which the small intestine empties its contents and is on the right side of the abdomen. The transverse colon runs along the upper abdomen. The descending colon promotes the content further downward on the left side. Finally, the sigmoid at the bottom ends a few more centimeters in the rectum. The stools leave the body through the anus.

About Colon & Rectal Polyposis

Colorectal cancer begins more frequently from a polyp, a non-cancerous tumor that may develop on the inner wall of the large intestine or rectum. If it won’t be treated or removed, a polyp can be potentially life-threatening because it can be transformed into cancer over time. Finding and removing precancerous polypuses can prevent the development of colorectal cancer.

There are many forms of polyps. The adenomatous polyps, or adenomas, are tumors that can become cancerous. They are identified by colonoscopy by a gastroenterologist (see Risk Factors).

Hyperplastic polyps can also develop in the colon and rectum and are not considered precancerous.

Most colorectal cancers (about 95%) are considered sporadic, which means that genetic mutations occur random after a person is born, so there is no risk of these genetic changes in children. The hereditary cancers of the colon intestine are less frequent (approximately 5%) and occur when gene mutations, inherited in a family from one generation to the next. Frequently, the cause of colorectal cancer is not known. However, the following factors may increase a person’s risk of developing colorectal cancer:

Age.

The risk of colorectal cancer increases as people get older. The cancer of the colon intestine can occur in young adults and adolescents, but the vast majority of colorectal cancers occurs in people over 50 years. For colorectal cancer the mean age at diagnosis at the time of diagnosis is 68 for men and 72 for women and 63 for men and women.

It is important to note that while colorectal cancer is still more commonly diagnosed in older adults, the incidence rate of colorectal cancer decreased by approximately 5% per year in adults of 65 years old and decreased by 1.4% per year in adults 50 to 64 years old, based on the latest statistics. Meanwhile, the incidence has increased by about 2% per year in adults under 50. The increase is largely due to the growing number of rectal cancers. About 11% of all cases of colorectal cancer are in people under the age of 50.

Sex.

Men have a slightly higher risk in developing colorectal cancer than women.

Family’s colorectal cancer history.

Colorectal cancer can be inherited in the family if the first-degree relatives (parents, brothers, sisters, children) or other family members (grandparents, uncles, nephews, grandchildren, cousins) had cancer of the large intestine. This is especially true when family members are diagnosed with colorectal cancer before the age of 60. If a person has a family history of colorectal cancer, the risk of developing the disease is almost double for that person. The risk is further increased if other close relatives have also developed colorectal cancer or if a first-degree relative was diagnosed at an early age.

It’s important to talk to your family members about the colorectal cancer’s history, if any. If you think you may have a family history of colorectal cancer, talk to a genetic counselor before doing any genetic testing. Only genetic tests can determine whether you have a genetic mutation and genetic counselors are trained to explain the risks and benefits of genetic testing.

Rare Inheritance.

Idiopathic Inflammatory Bowel Disease (IBD).

People with IBD, such as ulcerative colitis or Crohn’s disease, have an increased risk of developing colorectal cancer. IBD is not the same as Irritable Bowel Syndrome (IBS). IBS does not increase the risks of developing colorectal cancer.

Adenomatous Polyposis (adenomas).

Polyps are not cancer, but some types of polyps called adenomas can develop into colorectal cancer over time. Polyps can be removed using a tool during a colonoscopy, a test in which the gastroenterologist examines the colon using an illuminated tube. People with adenomas have a higher risk of developing additional polyps and colorectal cancer and should be monitored regularly.

Personal history of some types of cancer.

People with a personal history of colorectal cancer and women who have ovarian or uterine cancer are more likely to develop colorectal cancer.

Race.

Colored people have the highest rates of sporadic or non-hereditary colorectal cancer in the United States. Colorectal cancer is also the leading cause of death associated with cancer among people of color.

Physical inactivity and obesity.

People who do not exercise regularly and people who are overweight or obese may have an increased risk of colorectal cancer.

Diet.

Current research has consistently linked consumption of more red meat and processed meat with a higher risk of disease.

Smoking.

Recent studies have shown that smokers are more likely to die of colorectal cancer than non-smokers.

For most types of cancer, biopsy is the only sure way for the doctor to know if an area of ​​the body has cancer. In a biopsy, the doctor takes a small sample of tissue for histological examination in a pathological laboratory.

This list describes diagnostic options for this type of cancer. Not all of the tests listed below for each person are used. Your doctor will consider the following factors when choosing a diagnostic test:

The type of cancer that is suspected

Your symptoms

The age and general state of your health

The results of previous medical examinations

Colonoscopy. Colonoscopy allows the gastroenterologist to look into the entire rectum and colon. If a suspicious lesion appears then the doctor takes a tissue sample, a procedure called biopsy.

Biopsy. A biopsy is the removal of a small amount of tissue for histological examination in the microscope. Other tests may indicate that there is cancer, but only a biopsy can make a clear diagnosis of colorectal cancer. The pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues and organs for the diagnosis of diseases (histological examination). A biopsy can be done during a colonoscopy, or it can be done on any tissue that is removed during surgery.

Molecular examination of the tumor. Your doctor may recommend performing laboratory molecular tests on a tumor sample to identify specific genes, proteins, and other factors unique to the tumor. The results of these tests can help your doctor determine your treatment options.

All colon cancers should be screened for problems called a mismatch repair defect (dMMR). The purpose of this test is twofold. First, this test is a way of finding Lynch syndrome (see Risk Factors). Second, the results will be used to determine whether immunotherapy should be considered in patients with metastatic disease. This screening can be done either by using specific immunohistochemical stains on the biopsy or surgical tissue or by assays looking for mutations called microbial instability (MSI).

Additional diagnostic tests:

The tool that doctors use for staging the colorectal cancer is the TNM system. Doctors use the results of histological examination (pTNM) and imaging tests (MRI CAT scan, etc.) to answer the following questions:

Tumor (T-tumor): How large is the primary tumor? Where is it?

Lymph node (N- node): Has the tumor metastasized? If so, where and at how many lymph nodes?

Metastasis (M- metastasis): Has the cancer metastasized to other parts of the body? If so, where and to what extent?

The results are combined to determine the stage of cancer for each individual.

The following are details of each section of the TNM system for colorectal cancer:

The tumor (T)

Using the TNM system, the “T” plus a letter or number (0 to 4) is used to describe how deep the tumor has developed on the bowel wall. The stage can also be divided into smaller groups that help describe the tumor in more detail. Specific volume information is given below.

TX: The primary tumor cannot be evaluated.

T0: (T plus zero): No signs of colon or rectal cancer.

Tis: Refers to in situ carcinoma (also called in situ cancer). Cancer cells are found only in the epithelium or mucosal chorion, which are the upper layers that carry the inner wall of the colon or rectum.

T1: The tumor has developed in the submucosal coat, which is the layer of tissue under the mucosa of the large bowel.

T2: The tumor has developed in the muscle lining, a deeper, thicker layer of intestinal wall muscle.

T3: The tumor has grown and spread within the muscle and orogenic retina. The orthogonal retina is a thin layer of connective tissue and forms the outer covering of the large intestine.

T4a: The tumor has developed on the surface of the visceral peritoneum, which means it has developed and filtered through all layers of the large intestine.

T4b: The tumor has infiltrated other organs or structures.

Lymph nodes (N)

“N” in the TNM system means lymph nodes. Lymph nodes are tiny bean-shaped organs found throughout the body. Lymph nodes help the body fight off infections as part of the immune system. Lymph nodes near the colon and rectum are called peripheral lymph nodes. All others are distant lymph nodes located in other parts of the body.

NX: Regional lymph nodes cannot be evaluated.

NO (N plus zero): There is no proliferation in the peripheral lymph nodes.

N1a: There are cancerous cells located in 1 peripheral lymph node.

N1b: There are cancerous cells located in 2 or 3 peripheral lymph nodes.

N1c: There are nodules consisting of cancer cells located in structures near the colon that do not appear to be lymph nodes.

N2a: There are cancerous cells located in 4 to 6 peripheral lymph nodes.

N2b: There are cancerous cells located in 7 or more peripheral lymph nodes.

Metastasies (M)

The “M” in the TNM system describes cancer that has spread to other parts of the body, such as the liver or lungs. This is called distant metastasis.

M0 (M plus zero): The disease has not spread to a distant part of the body.

M1a: The cancer has spread to another part of the body apart from the colon or rectum.

M1b: Cancer has spread to more than 1 part of the body except the colon or rectum.

M1c: Cancer has spread to the peritoneal surface.

It is important to remember that the symptoms of colorectal cancer listed in this section are the same as those of the most common non-cancerous conditions, such as hemorrhoids and irritable bowel syndrome (IBS). Early detection of the disease makes successful treatment more likely. However, many people with colorectal cancer have no symptoms until the disease progresses, so people should be examined regularly.

People with colon cancer may experience the following symptoms. As mentioned above, it is also possible that these changes can be caused by a non-cancer pathological condition, especially for the general symptoms of abdominal distress, bloating and irregular bowel movements.

Diarrhea, constipation or the feeling that the gut is not completely empty

Vivid red or very dark blood in the stool

Stools that look narrower or thinner than normal

Constipation, including frequent pain from gas, bloating, fullness

Unexplained Weight Loss

Constant fatigue or malaise

Unexplained anemia with iron deficiency

Talk to your doctor if any of these symptoms last for several weeks or become more severe. If you are concerned about any changes you are experiencing, please talk to your doctor and ask to schedule a colonoscopy.