Colorectal cancer is the fourth most common cancer in both men and women in the United States, according to the National Cancer Society. Colorectal cancer refers to the cancer that begins in the colon or rectum, both of which are located in the latter part of the large intestine. Because cancer in these two structures has many similar features, they are often referred to together, by the term "colorectal cancer." There are several types of colorectal cancer, which differ based on what type of cell in the colon or rectum becomes cancerous.
Adenocarcinoma
Adenocarcinomas are the most common type of colorectal cancer, making up 95 percent of all colorectal cancer cases, according to the American Cancer Society. This type of cancer begins in the cells of the colon and rectum that secrete mucus, which serves to lubricate the inside of the gastrointestinal tract and facilitate the movement of waste through this long tube.
Carcinoid Tumors
The American Cancer Society states that carcinoid tumors are a rare type of cancer that stem from specialized cells of the gastrointestinal tract called neuroendocrine cells. These cells are in some ways like nerve cells, and in other ways like hormone-producing cells. Though some neuroendocrine cells are located in the lungs, they are mostly in the gastrointestinal tract. Thus, most neuroendocrine cancers grow in the gastrointestinal tract. When a neuroendocrine cell becomes cancerous and forms a well-differentiated tumor in the colon or rectum, it is called a colorectal carcinoid tumor.
Hereditary Nonpolyposis Colorectal Carcinoma
A defective gene that is inherited from generation to generation causes this type of colorectal cancer, according to Merck Manuals, an online medical library. Though not many people have this gene mutation, it causes cancer in 70 to 80 percent of the people that do have it, often before the age of 50. The National Cancer Society adds that this type of cancer accounts for 2 percent of all colorectal cancer cases.
Gastrointestinal Stromal Tumors
Gastrointestinal stromal tumors stem from cells located in the colon wall, which are called the "interstitial cells of Cajal." While the American Cancer Society states that these tumors can occur anywhere in the gastrointestinal tract, they most commonly grow in the colon. Furthermore, these tumors may be malignant, meaning cancerous, or benign, meaning noncancerous.
