Colorectal carcinoma
What is it?
Colorectal cancer is defined as a growth of malignant cells in the large intestine (cecum and colon), i.e., the last part of the intestine, or in the rectum/anus. Therefore, it is more common to talk about colon cancer or rectal cancer. There are also forms starting in the small intestine, but they are very rare.
The colon and rectum represent the so-called "large intestine," the terminal part of the gastro-intestinal tract. The colon measures more than one meter and the rectum, which is the part of the large intestine that ends in the anus, is about 15 centimeters long.
Among neoplasms of the large intestine, carcinoma - which is by far the most common form - originates from the mucosa (the inner part of the intestine) often by malignant transformation of polyps and develops by infiltrating the wall of the intestine.
There are different types of colorectal cancer, which can be identified by their histology, i.e. by analyzing the microscopic structure of the cancer cells.
- adenocarcinoma: this is the most common type of colorectal cancer that accounts for about 95% of cases. It develops from the glandular cells lining the inner surface of the colon or rectum;
- squamous cell carcinoma: this type of cancer is very rare and accounts for less than 1% of colorectal cancer cases. It develops from the flat cells lining the inner surface of the colon or rectum;
- neuroendocrine carcinoma: this type of cancer develops from neuroendocrine cells in the colorectum, which produce hormones and other substances that regulate the endocrine system. This type of cancer is very rare and can be more difficult to diagnose and treat than other subtypes;
- stromal tumors: neoplasms that develop from the stromal cells of the intestine, which are responsible for the formation of connective tissue and blood vessels. These tumors are also known as GISTs (Gastrointestinal Stromal Tumors) and are the most common type of connective tissue tumors of the intestine;
- lymphomas from gut lymphoid tissue;
- melanomas from gut melanocytic cells.
Causes and risk factors
There are several risk factors associated with the development of colorectal cancer. Some of these factors can be changed, while others cannot be controlled:
- age: the risk of developing colorectal cancer increases with age. Most cases of colorectal cancer occur in people over the age of 50;
- family history: people with a family history of colorectal cancer or precancerous polyps have an increased risk of developing the cancer. The risk is even greater if a first-degree relative (mother, father, brother, or sister) has had the disease;
- personal history of polyps or colorectal cancer: people who have already had precancerous polyps or colorectal cancer have an increased risk of developing the disease again;
- chronic inflammatory bowel disease such as ulcerative colitis or Crohn's disease;
- presence of pathogenic variants (mutations) that predispose to the development of cancer (e.g., Lynch syndrome; familial adenomatous polyposis, genetic minor polyposis);
- "Western" type diet, or the Western dietary pattern, rich in fat and processed meat, and low in fiber, fruits and vegetables;
- poor lifestyle: physical inactivity, obesity, cigarette smoking;
- other factors such as ethnicity and type II diabetes.
Which are the symptoms?
Colorectal cancer often has no symptoms in the early stages of the disease, but when symptoms occur they may include:
- blood in the stool;
- changes in bowel habits, such as diarrhea or persistent constipation;
- abdominal pain, bloating or cramping;
- sensation of not emptying the rectum completely after evacuation;
- weakness or fatigue;
- unexplained weight loss.
However, many of these symptoms can be caused by other conditions, so it is important to consult a doctor if you suspect you have an intestinal problem.
How is it diagnosed?
The diagnostic pathway for colorectal cancer may include several tests and procedures. The process may vary depending on the patient's symptoms and risk factors for colorectal cancer. However, in general, diagnostic steps may include:
- physical examination: the physician will examine the patient's abdomen, rectum, and anus for any masses or abnormalities;
- blood test: the doctor may request a blood test to check for colorectal cancer-associated tumor markers and anemia;
- stool test for occult blood: this test detects the presence of blood in stool that is not visible to the naked eye;
- colonoscopy: this test uses an endoscope with a camera at the end (colonoscope) to examine the entire colon;
- biopsy: If a suspicious mass or area is detected during colonoscopy, a biopsy may be performed to take a tissue sample for later analysis;
- diagnostic scan: If the cancer has already been diagnosed, the doctor may request a diagnostic scan, such as a CT scan or MRI, to determine the extent of the tumor and whether it has spread to other parts of the body.
The diagnostic pathway may vary depending on the severity and type of colorectal cancer. The doctor will guide the patient through the appropriate tests and examinations to determine the best diagnosis and treatment for his or her condition.
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How is it treated?
Colorectal cancer can be treated with different therapies: medical, surgical, and radiation therapy. The choice of treatment depends on the location, stage and characteristics of the tumor, as well as the patient's health condition:
- Surgery: often the primary therapy for colorectal cancer. It may involve removal of part of the colon (colectomy), the entire colon (total proctocolectomy) or the rectum (anterior resection of the rectum). Sometimes, other surrounding tissues and organs may also need to be removed;
- Chemotherapy: uses drugs to destroy cancer cells. It is often used after surgery to reduce the risk of recurrence, but it can also be used before surgery to reduce the size of the tumor. Chemotherapy can be administered intravenously or orally;
- Radiation therapy: uses high-energy radiation to destroy cancer cells. It can be used before surgery to reduce the size of the tumor or after surgery to destroy any remaining cancer cells. Radiation therapy can be administered externally or internally, using radioactive sources;
- Targeted therapy: uses drugs to attack specific signaling molecules that promote cancer cell growth. These drugs can be used in combination with chemotherapy or radiation therapy;
- Immunological therapy: uses drugs to stimulate the immune system to recognize and attack cancer cells.
Treatment of colorectal cancer often requires a combination of these options. The doctor will guide the patient in choosing the best treatment based on his or her specific condition.
Suggested procedures
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