Colorectal cancer (also known as colon cancer, rectal cancer, bowel cancer or colorectal adenocarcinoma) is cancer from uncontrolled cell growth in the colon or rectum (parts of the large intestine), or in the appendix.

Genetic analysis shows that essentially colon and rectal tumors are genetically the same cancer.

Symptoms of colorectal cancer typically include rectal bleeding and anemia which are sometimes associated with weight loss and changes in bowel habits.

Most colorectal cancer occurs due to lifestyle and increasing age with only a minority of cases associated with underlying genetic disorders. It typically starts in the lining of the bowel and if left untreated, can grow into the muscle layers underneath, and then through the bowel wall.

Screening is effective at decreasing the chance of dying from colorectal cancer and is recommended starting at the age of 50 and continuing until a person is 75 years old. Localized bowel cancer is usually diagnosed through sigmoidoscopy or colonoscopy.

Cancers that are confined within the wall of the colon are often curable with surgery while cancer that has spread widely around the body is usually not curable and management then focuses on extending the person’s life via chemotherapy and improving quality of life.

Colorectal cancer is the third most commonly diagnosed cancer in the world, but it is more common in developed countries. Around 60% of cases were diagnosed in the developed world.

The symptoms and signs of colorectal cancer depend on the location of the tumor in the bowel, and whether it has spread elsewhere in the body (metastasis).

The classic warning signs include worsening constipation, blood in the stool, decrease in stool caliber, loss of appetite, loss of weight, and nausea or vomiting in someone over 50 years old.

While rectal bleeding or anemia are high-risk features in those over the age of 50, other commonly-described symptoms including weight loss and change in bowel habit are typically only concerning if associated with bleeding.

Diagnosis

Diagnosis of colorectal cancer is via tumor biopsy typically done during colonoscopy or sigmoidoscopy, depending on the location of the lesion.

The extent of the disease is then usually determined by a CT scan of the chest, abdomen, and pelvis. There are other potential imaging tests such as PET and MRI which may be used in certain cases.

Colon cancer staging is done next and based on the TNM system which is determined by how much the initial tumor has spread, if and where lymph nodes are involved, and if and how many metastases there are.

The histology of the tumor is usually reported from the analysis of tissue taken from a biopsy or surgery.

A pathology report will usually contain a description of cell type and grade. The most common colon cancer cell type is adenocarcinoma which accounts for 95% of cases. Other, rarer types include lymphoma and squamous cell carcinoma.

The treatment of colorectal cancer can be aimed at curation or palliation. The decision on which aim to adopt depends on various factors, including the patient’s health and preferences, as well as the stage of the tumor. When colorectal cancer is caught early, surgery can be curative.

However, when it is detected at later stages for which (metastases are present), this is less likely and treatment is often directed at palliation, to relieve symptoms caused by the tumor and keep the person as comfortable as possible.

For people with localized cancer, the preferred treatment is complete surgical removal with adequate margins, with the attempt of achieving a cure. This can either be done by an open laparotomy or sometimes laparoscopically.

If there are only a few metastases in the liver or lungs they may also be removed. Sometimes chemotherapy is used before surgery to shrink the cancer before attempting to remove it. The two most common sites of recurrence of colorectal cancer are in the liver and the lungs.



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