Types of Rectal Cancer

The vast majority of rectal cancers are adenocarcinomas. These are cancers of the cells that line the inside surface of the rectum. Rarer tumor types include: 

  • carcinoid tumors, which start in hormone-producing cells in the intestines
  • gastrointestinal stromal tumors, a type of soft tissue sarcoma that can be found anywhere in the gastrointestinal tract but is rare in the rectum, or other types of sarcoma that start in the blood vessels or connective tissue in the colon
  • lymphomas, which are cancers of the immune system that more commonly start in the lymph nodes but can start in the rectum

These types may be treated differently than adenocarcinomas. This section on the diagnosis and treatment of rectal cancer refers primarily to adenocarcinomas.

About 5 to 10 percent of colorectal cancers are hereditary (due to specific mutations in the genes that are passed from parents to children). Based on your personal risk, our rectal cancer experts may offer you genetic testing to see if you have mutations in your genes that can increase your cancer risk. This is based on an assessment of your personal risk. Learn more about genetic testing for rectal cancer and the types of hereditary conditions that often lead to the disease.