Colorectal cancer is a malignant neoplastic disease of the colon and rectum. It is he who is often referred to when talking about bowel cancer. He owns one of the first places in the line of the most frequently detected malignant neoplasms today.
With the progression of the pathological process, the lesion spreads into the intestinal lumen, or the tumor grows into the surrounding tissues. The disease can be accompanied by metastasis, so early diagnosis is especially important, due to which the chances of effective treatment of bowel cancer increase. The risk of colorectal cancer increases after the age of 45, reaching a maximum by the age of 70-75, and to a greater extent in men.
Intestines - an organ whose main function is to digest food, is divided into two sections: the small intestine and the large intestine. This article will focus on colon cancer.
The human large intestine, in turn, consists of six sections: the cecum, four sections of the colon (ascending, transverse, descending, sigmoid colon) and the rectum. A malignant tumor can form in any of them, but the most common cancer is the rectum - the final section of the intestine, in which feces accumulate and are excreted.
Causes of colon cancer
When the cells of the mucous membrane of the colon or rectum fail and begin to divide uncontrollably, a tumor is formed that grows, disrupts the integrity of tissues, organs and functions of the body. Risk factors for bowel cancer are age, heredity, benign polyps, chronic inflammation, excess weight, bad habits and poor diet. Smokers, drinkers, the elderly, people with obesity and with relatives who have been diagnosed with bowel cancer or familial adenomatous polyposis are more likely to suffer from this disease than others.
Two main factors can contribute to the appearance of cancer of the rectum or other part of the colon: nutritional errors and hereditary predisposition. The main dietary disorders that cause colorectal cancer include the following:
- Lack of dietary fiber.
- Excess or predominance of animal fats in the daily menu.
- Overeating.
- Alcohol abuse.
Fiber-rich foods that are low in saturated fats and trans fats have an anti-carcinogenic effect. Reduces the risk of colon cancer food rich in vitamins D, C, calcium.
Numerous scientific studies confirm the predisposition to colorectal cancer at the genetic level. Scientists especially highlight the relationship of mutations at the gene level with the development of polyposis and non-polyposis hereditary cancer. Changes are observed in the MLH1 and MSH2 genes, therefore, if these abnormalities are detected, the whole family should undergo a thorough diagnosis. Those at risk should be screened for colorectal cancer periodically to detect cancer at an early stage.
Other causes of colorectal cancer include:
- Polyps, adenomas, other benign neoplasms of the colon.
- Crohn's disease
- Chronic colitis.
- Reduced immunity.
- Exposure to carcinogens.
- Chronic infections.
- Human papillomavirus.
- Tumors of the female genital area, breasts.
- Inflammatory bowel disease in a chronic condition.
The presence of several factors that affect the body for a long time is especially dangerous. Cancer often forms in the place of polyps, which over time can become malignant.
Risk factors for colorectal cancer may also include age over 55 years (for colorectal cancer - 63 years), a sedentary lifestyle, smoking and alcoholism. Certain conditions, such as diabetes, acromegaly, or gallstones, also increase the chance of developing colorectal cancer.
All of the above causes and risk factors can cause mutations in intestinal cells. And some of these mutations can lead to malignant tumors. The state of a cell in which the risk of mutations under the influence of certain factors is higher than usual is called microsatellite instability. This instability is the cause of colorectal cancer in 5% of cases and can lead to defects in chromosomes or DNA repair systems. Microsatellite instability in colorectal cancer lies in the fact that in the DNA of intestinal cells there are genes, mutations in which lead to the development of neoplasms. A lot of scientific literature has been written about the mechanisms of the occurrence of these mutations and the development of colorectal cancer, thanks to which it is possible to find an effective method of treatment in each specific case.
Types of colon cancer
Malignant tumors of the colon according to the characteristics of their growth can be divided into:
- exophytic - tumors grow vertically, into the lumen of the colon;
- endophytic - tumors grow horizontally, inside the wall of the colon;
- Mixed tumors - combine both types of growth.
Benign tumors of the colon include tubular adenoma, tubular-villous adenoma, villous tumor, adenomatous polyp of the colon. They also pose a danger and require regular examinations from the patient, since colon cancer can develop against the background of these benign neoplasms.
According to histological characteristics (according to the type of cells from which the tumor was formed), colon cancer is divided into the following types: adenocarcinoma, squamous cell carcinoma, solid formation, melanoma, high-density carcinoma (scirrhous cancer), cricoid colon cancer. In most cases, adenocarcinoma occurs, which is formed in the cells of the inner surface of the colon or rectum.
By the degree of cell differentiation (i.e., by how similar the tumor cells are to those from which they formed), colon cancer can be divided into:
- well-differentiated neoplasms - cells of a malignant tumor are very similar to healthy cells from which they were formed;
- moderately differentiated;
- poorly differentiated;
- undifferentiated - tumor cells are very different from healthy colon cells.
Metachronous cancer is a multiple cancer in which two or more primary tumors develop. Metachronous sigmoid colon cancer is the most common. Then comes metachronous rectal cancer.
Signs of colorectal cancer
As often happens with oncological diseases, bowel cancer can develop gradually and for a long time a malignant tumor does not make itself felt. This is exactly the time period when early diagnosis of colon cancer helps to prescribe effective, correct treatment in time, followed by a complete recovery of the patient. Unfortunately, colorectal cancer often makes itself felt at the stages when the tumor has already grown into the intestinal wall, metastases are formed. Therefore, it is important to pay attention to even the slightest signs of colorectal cancer.
In the early stages, colon cancer has no symptoms, but as the cancer grows, pain, increased gas formation, a feeling of heaviness, bloating, and irregular stools begin to appear.
Warning symptoms that should promptly seek medical attention include the following:
- Blood in the stool.
- Changes in stool regularity, frequent constipation, diarrhea.
- Isolation of mucus from the anus.
- Pain in the abdomen, anus.
- Unexpected weight loss.
- The appearance of symptoms associated with anemia, such as pale skin, shortness of breath, increased heart rate, lethargy, drowsiness.
- Weakness during the day.
- Painful urge to defecate.
Similar symptoms appear with metachronous colon cancer, especially weakness, pain, and discharge with blood and/or mucus. With cancer of the sigmoid colon, mucus and blood envelop the stool, and with cancer of the caecum, they mix with the masses. With colon cancer, tarry stools appear.
Symptoms of anemia are associated with cancer of the ascending colon. Tumors in this area can disrupt the body's hematopoietic functions.
It is important to pay maximum attention to the appearance of any of the described symptoms of colorectal cancer, which you should definitely tell the doctor during the consultation. A qualified and experienced doctor will definitely try to clarify in a delicate form the fact of the presence of dangerous symptoms during the survey, which will make it possible to detect key signs of colon cancer.
Constipation and diarrhea, pain, blood in the stool, as well as false urges, nausea and vomiting, fluid in the abdominal cavity - all these are symptoms of colon cancer in the later stages of development.
The symptoms of colorectal cancer do not differ between men and women. In addition to those described above, patients with colorectal cancer may also suffer from headaches, decreased performance, decreased appetite, etc. Unfortunately, malignant tumors in the colon can develop for more than ten years and do not manifest themselves for years.
At an early stage, in the absence of a pronounced clinical picture, today only preventive colonoscopy will help eliminate the risk or detect colorectal cancer, which is recommended after 45-50 years, especially those at risk.
Colorectal cancer stages
The degree of neoplasm development is determined by its prevalence relative to the intestinal wall. The severity of the clinical picture, the prognosis for treatment depends on this. There are 4 stages of colorectal cancer:
- Stage I colon cancer. The tumor process is located within the intestinal wall. The patient does not complain, mucus may be released during defecation. Cancer cells do not affect regional lymph nodes, there are no metastases. With timely treatment, the prognosis for recovery is favorable.
- Stage II colorectal cancer. The focus extends to all the walls of the colon, germination of nearby fiber is possible. Metastases are not found. Among the signs of colon cancer is discomfort in the rectal region, compared with the appearance of a foreign body. There are unpleasant sensations in the lower abdomen, blood can be added to the mucus in the stool.
- Stage III colon cancer. Due to the increase in tumor formation, the patency of the rectum is impaired. The stage proceeds without or with the presence of metastases in the regional lymph nodes surrounding the rectum. The neoplasm grows into the surrounding tissues, fiber, neighboring organs, and more distant lymph nodes. The patient's condition worsens, and such disorders as bloating, rumbling in the abdomen, and false urge to defecate are added to the existing manifestations. Complaints relate to pain, spasms, inclusions in the stool of blood, diarrhea, constipation. Against the background of progressive colon cancer, general weakness increases, efficiency decreases, appetite decreases, pallor is fixed.
- IV terminal stage of colorectal cancer, at which the development of a malignant tumor reaches its maximum volume. The risk of stopping the functioning of the intestine, the activity of nearby organs increases. Metastases spread to distant lymph nodes, lungs, liver, bones, stomach. Severe clinical manifestations of colon cancer are intestinal obstruction, vomiting, constipation, gas retention. The patient complains of abdominal pain, projections of the location of organs affected by cancer cells. There is a pronounced depletion of the body, signs of damage to the central nervous system.
The TNM system for determining the stage of intestinal cancer determines the extent of the spread of the tumor and the presence of metastases in the nearest lymph nodes and other parts of the body:
- T - the degree of spread of the primary malignant tumor: T1 - the tumor has affected the intestinal mucosa, T2 - it has spread to the muscle layer, T3 - all layers of the intestine are affected, T4 - the malignant tumor grows into neighboring tissues and organs.
- N - the number of affected regional lymph nodes: N0 - the tumor did not affect the lymph nodes, N1 - there are metastases in 1 - 3 lymph nodes, N2 - in four or more lymph nodes;
- M - the presence of distant metastases: M0 - they are absent, M1 - distant metastases are present.
Possible complications of colon cancer
- Obstructive intestinal obstruction. At various stages of the disease, it can be partial or complete.
- Bleeding from the tumor focus - occurs against the background of the collapse of the neoplasm. The consequence is more characteristic of exophytic growth of a malignant tumor. If there are blood vessels in the decay zone, they collapse and cause blood loss, which is accompanied by signs of anemia. Blood of scarlet or dark color begins to stand out from the anus. Severe blood loss leads to dizziness, weakness, and the skin becomes pale. The condition is aggravated by increased heart rate, tinnitus, shortness of breath, loss of consciousness in severe cases.
- Growth of colon cancer to adjacent organs. If it is the bladder, there are changes in the urine, such as the appearance of turbidity, fecal impurities, inflammation directly in the bladder. The patient complains of burning, pain during urination, feeling of incomplete emptying of the bladder. A striking manifestation of the complication of cancer is the leakage of urine from the anus. If colorectal cancer is diagnosed in a woman, enterovaginal fistulas can become a complication. At the same time, feces, gases, and mucous discharges with an unpleasant odor and a cloudy color begin to stand out from the vagina.
- Inflammatory changes in adjacent tissues.
- All of the described complications are formed in the later stages of colon cancer.
