Generally, the inflammatory condition of the gut is known for increasing the risk of colorectal cancer. Notable examples are ulcerative colitis and Crohn’s disease. However, while conducting a follow-up study for determining the risk of colorectal cancer due to microscopic colitis, no increased risk for cancer was found.
Can Microscopic Colitis Cause Cancer?
Microscopic colitis is a condition of inflammation in the colon leading to watery diarrhea and other related symptoms such as abdominal pain, bloating, flatulence, nausea, muscle pain and joint pain. However, it is different form the other inflammatory condition of the gastrointestinal tract as it can not be seen without the help of the microscope. Various studies have been conducted to study the risk of cancer that microscopic colitis carries in comparison to other inflammatory condition. Almost all the studies have found that there is no connection between the microscopic colitis and colorectal cancer.
This indicates that the risk of developing cancer in patients with microscopic colitis is equal to those who are not having microscopic colitis. However, it has been found that women with collagenous colitis carries increased risk of lung cancer. The mechanism behind this phenomenon remains unknown. Unlike ulcerative colitis and Crohn’s disease, which are known for increasing the risk of colorectal carcinoma and celiac disease which has the increased risk of lymphoproliferative disorders and esophageal cancer, microscopic colitis does not carry the risk of malignancy. In some studies, the follow-up of the patients, after the diagnosis of colitis, is done for at least 7 years and no colorectal cancer was noted.
Although the explanation to no increased risk of colorectal cancer due to microscopic colitis as compared to other inflammatory condition such as ulcerative colitis and Crohn’s disease is unknown. This may possibly be due to the poor absorption of the carcinogens or other fat soluble agents. Another hypothesis may be that the immunological alterations in microscopic colitis may do not allow the malignancies to occur. It is due to the immunological surveillance done by the lymphocytes which does not allow the cancer cells to grow and hence does not increases the risk of cancer. This action of lymphocytes is of primary importance in case of skin. Also, the human intestinal cells also contain different type of natural killer cells which are not found in blood. Further, certain antidiarrheal drugs administered during microscopic colitis also reduces the risk of cancer. The NSAIDs also reduces the risk of cancer in these patients. It has been postulated that presence of microscopic colitis may itself reduces the risk of cancer by an unknown mechanism. It has also been found that the patients who are having the past history or the present case of malignancy are more like to develop microscopic colitis.
Types of Microscopic Colitis
The microscopic colitis is divided in to two types on the basis of presence of causative factor of inflammation. The two types are:
Lymphocytic Colitis: This condition was first described in 1989. It is characterized by the accumulation of lymphocytes in the colonic epithelium and connective tissue. The presence of lymphocytes in the colonic epithelium results in inflammation which can be on the microscopic anatomy.
Collagenous Colitis: This condition is characterized by the deposition of collagen in the colon epithelium.
Some researchers believe that both the conditions exit at different phases of the disease. Initially, there is an infiltration of lymphocytes which may lead to deposition of collagen. But there is no study to support this belief.
The infiltration of lymphocytes and deposition of collagen leads to watery diarrhea without any bleeding.
As the other inflammatory conditions of the gastrointestinal tract such as ulcerative colitis and Crohn’s disease increase the risk of colorectal cancer, studies were conducted to conclude the effect on risk of cancer due to microscopic colitis. None of the studies concluded the increased risk of colorectal cancer due to microscopic colitis. It has been postulated that there are certain mechanisms related to the condition, which reduces the risk of cancer in such patients.