Adenocarcinoma of the colon is a malignant neoplasm that develops from the cells of the glandular epithelium. In the early stages, it proceeds with erased clinical symptoms. With progression, weakness, abdominal pain, a feeling of incomplete bowel emptying, stool disorders, tenesmus, lack of appetite, weight loss, fever to subfebrile numbers, mucus and blood in the stool are observed. Intestinal obstruction is possible. The diagnosis is established on the basis of complaints, objective examination data and the results of instrumental studies. Treatment is surgical removal of the tumor.
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Adenocarcinoma of the colon is a cancer that develops from epithelial cells. It makes up about 80% of the total number of malignant tumors of the large intestine. In 40% of cases, it affects the cecum. It ranks fourth in prevalence among oncological diseases in women and third in men, second only to stomach, lung and breast cancer. It occurs more often after the age of 50.
The probability of adenocarcinoma increases with various conditions and diseases accompanied by impaired peristalsis and deterioration of blood supply to the large intestine. In the initial stages, the disease usually proceeds asymptomatically or with mild nonspecific clinical symptoms, which complicates diagnosis and reduces the survival rate. The treatment is carried out by specialists in the field of oncology.
It is assumed that adenocarcinoma of the colon develops as a result of a combination of several unfavorable factors, the main of which are somatic diseases, diet features, some environmental parameters and unfavorable heredity. An increased likelihood of malignant tumors is noted in colon polyps. The somatic diseases that provoke adenocarcinoma include ulcerative colitis, Crohn’s disease, as well as pathologies accompanied by chronic constipation and the deposition of fecal stones.
Many researchers point to the importance of dietary factors. The likelihood of colon adenocarcinoma increases with a lack of plant fiber in food and the use of a large number of meat products. Scientists believe that plant fiber increases the volume of feces and accelerates their progress through the intestine, limiting the contact of the intestinal wall with carcinogens formed during the breakdown of fatty acids. This theory is very close to the theory of the development of adenocarcinoma under the influence of carcinogens that appear in food during improper heat treatment of products.
Environmental factors include too active use of household chemicals, occupational hazards, sedentary work and a sedentary lifestyle. Adenocarcinoma of the colon often occurs with hereditary familial cancer syndrome (after 50 years, every third carrier of the gene becomes ill), in the presence of malignant neoplasms in close relatives and with some non-oncological hereditary diseases (for example, Gardner syndrome).
Adenocarcinoma of the colon pathogenesis
The tumor develops according to the general laws of growth and spread of malignant neoplasms. It is characterized by tissue and cellular atypism, a decrease in the level of cell differentiation, progression, unlimited growth and relative autonomy. At the same time, adenocarcinoma of the colon has its own characteristics. It does not grow and develop as fast as some other malignant tumors, and remains within the intestine for a long time.
The development of neoplasms is often accompanied by inflammation that spreads to nearby organs and tissues. Cancer cells penetrate into these organs and tissues, forming nearby metastases, while distant metastasis may be absent. Neoplasia most often metastasizes to the liver and lymph nodes, although other localization of distant metastases is possible. Another feature of the disease is the frequent simultaneous or sequential formation of several tumors in the large intestine.
Taking into account the level of cell differentiation , three types of colon adenocarcinoma are distinguished: highly differentiated, moderately differentiated and low-differentiated. The lower the level of cell differentiation– the more aggressive the tumor growth and the higher the tendency to early metastasis. To assess the prognosis for colon adenocarcinoma, oncologists use the international classification TNM and the traditional Russian four-stage classification. According to the Russian classification:
- Stage 1 – the neoplasm does not go beyond the mucous membrane.
- Stage 2 – the tumor sprouts the intestinal wall, but does not affect the lymph nodes.
- Stage 3 – the neoplasm sprouts the intestinal wall and affects the lymph nodes.
- Stage 4 – distant metastases are detected.
Adenocarcinoma of the colon symptoms
In the early stages, adenocarcinoma of the colon is asymptomatic. Since pathology often develops against the background of chronic intestinal diseases, patients may interpret the symptoms as another exacerbation. Possible stool disorders, general weakness, periodic abdominal pain, decreased appetite, the appearance of impurities of mucus or blood in the stool. When the lower parts of the large intestine are affected, the blood is scarlet, located mainly on the surface of the fecal masses.
When an adenocarcinoma is located in the left half of the intestine, the blood is dark, mixed with mucus and feces. When the neoplasm is localized in the right half of the intestine, bleeding is often latent. As the tumor grows, the symptoms become more pronounced. Patients with colon adenocarcinoma are worried about intense pain. Severe fatigue develops. Anemia, fever to subfebrile numbers and aversion to meat food are observed.
Diarrhea and constipation become permanent, do not go away when using medications. Adenocarcinoma of the colon creates a mechanical obstacle to the movement of fecal masses and causes frequent tenesmus. The pressure of feces on the tumor causes its ulceration, and the formation of ulcers leads to increased bleeding and the development of inflammation. Pus appears in the feces. The temperature rises to febrile numbers. Signs of general intoxication are detected.
Many patients have jaundice of the skin and icteric sclera. When the inflammatory process spreads to the retroperitoneal tissue, pain and muscle tension occur in the lumbar region. Intestinal obstruction is possible (especially in adenocarcinomas with exophytic growth). In the later stages, ascites and liver enlargement are detected. Sometimes abdominal symptoms are absent, the tumor manifests itself for a long time only by weakness, increased fatigue, weight loss and decreased appetite.
The diagnosis of colon adenocarcinoma is established by specialists in the field of clinical oncology on the basis of complaints, anamnesis, general examination and finger examination of the rectum and the results of instrumental studies. More than half of the tumors are located in the lower parts of the large intestine and are detected during finger examination or rectoromanoscopy. With a high localization of the neoplasm, a colonoscopy is necessary. During endoscopy, the doctor takes a sample of tumor tissue for subsequent histological examination, which allows to verify the tumor.
To assess the size, shape and prevalence of adenocarcinoma, X-ray contrast examination of the large intestine (irrigoscopy) is used. Ultrasound techniques are used to detect metastases and in the presence of contraindications to endoscopic examinations, for example, with bleeding. In complex cases, a patient with suspected colon adenocarcinoma is referred to an abdominal MSCT. The patient is prescribed general blood and urine tests, a biochemical blood test and a stool test for hidden blood. The final diagnosis is made after examining the biopsy.
Adenocarcinoma of the colon treatment
Treatment of neoplasia is operative. An important element of treatment is preoperative preparation, which makes it possible to restore the continuity of the large intestine and minimize the number of complications. The patient is prescribed a slack-free diet and laxatives. A few days before the operation, cleansing enemas begin to be performed. In recent years, washing of the gastrointestinal tract with the use of special drugs has often been used.
The volume of radical surgical intervention in adenocarcinoma is determined taking into account the size and location of the malignant neoplasm, the presence or absence of regional metastases:
- Resection with anastomosis. If possible, colon resection is performed, and then an anastomosis is created, restoring the integrity of the intestine.
- Resection with a colostomy. With a significant tension or low location of the tumor, a colostomy is applied after resection of the affected area.
- Palliative colostomy. In case of inoperable cancer and intestinal obstruction, palliative colostomy is performed.
In case of distant metastases, palliative surgical interventions are also performed to prevent complications (bleeding, intestinal obstruction, intense pain syndrome).
Adenocarcinoma of the colon prognosis and prevention
When detecting colon adenocarcinoma at stage 1, the five-year survival rate is about 90%. If treatment is started at stage 2, 80% of patients overcome the five-year survival threshold. At stage 3, the survival rate decreases to 50-60%. If the rectum is affected, the prognosis worsens.
After surgery, patients are placed under observation, it is recommended to regularly examine the feces for the presence of blood and mucus. Rectoromanoscopy or colonoscopy is performed quarterly. Once every 6 months, patients are referred for ultrasound of internal organs to detect distant metastases. About 85% of recurrences of colon adenocarcinoma occur in the first two years after surgery.