Rectal cancer is commonly classified as colorectal cancer, along with colon cancer. Rectal cancer develops in cells in the rectum, located below the colon and above the anus.
Rectal and colon cancers are often grouped together under the umbrella term colorectal cancer, as the rectum and colon are both parts of the digestive system. Colorectal cancer is the second most common cancer in females and the third most common cancer in males globally.
In the United States, there is a high prevalence of colorectal cancer. The American Cancer Society estimated that in 2020 there were 43,340 new cases of rectal cancer and 104,610 new cases of colon cancer.
There are various types of rectal cancer which we break down below. The majority of rectal cancer diagnoses are adenocarcinoma. There are also rarer types of tumors that require different treatments.
The majority of rectal cancer cases are adenocarcinoma which affects the cells lining the inside surface of the rectum.
Carcinoid tumors occur in hormone-producing cells within the intestines.
Gastrointestinal stromal tumors
Gastrointestinal stromal tumors are rarely found in the rectum, but they can be found anywhere in the gastrointestinal tract. They are thought to arise from the ‘pacemaker cells’ of the gastrointestinal tract.
Lymphoma is classified as a cancer of the immune system. While it commonly starts in the lymph nodes, lymphoma can also start in the rectum.
Hereditary rectal cancer
5-10% of patients develop colorectal cancer due to specific mutations in their inherited genes, referred to as hereditary mutations. For individuals at high risk, genetic testing is advisable to determine whether you have genetic mutations that can increase your cancer risk.
There are five stages of rectal cancer, labeled from 0 to IV. Generally, the lower the number, the less the cancer cells and tumors have spread.
At the lowest stage of rectal cancer, cancer cells are only found in the innermost lining of the rectum wall, called the mucosa.
The tumor has now spread beyond the inner lining but remains within the rectum wall and has not spread to the lymph nodes. Lymph nodes are small filter-like organs that form part of the immune system.
Cancer extends through the outer muscle layer of the rectum but has still not spread to the lymph nodes.
Cancer has now spread to lymph nodes outside the rectum.
Cancer has continued to spread to other organs, tissues, and parts of the body,