What is colorectal cancer?

Colorectal cancer includes colon and rectal cancers. Most colorectal cancers start as a growth of polyps on the inner lining of the colon or rectum and can slowly change into cancer over time. Not all polyps become cancer. The chance of a polyp becoming cancerous depends on its type. Two main kinds include:

  • Adenomatous polyps (adenomas) – sometimes develop into cancer. Because of this, adenomas are referred to as pre-cancerous condition.
  • Hyperplastic polyps and inflammatory polyps – are common, but generally not pre-cancerous.

Colorectal cancer starts in the innermost layer (the mucosa) of the colon or rectum and can grow outward through other layers. It can travel to other parts of the body such as blood vessels, lymph vessels, lymph nodes, or further. The extent of spread outside the walls of the colon and rectum is referred to as staging. Your medical oncologist will discuss the specifics of your stage and treatment options with you.

More information about colorectal cancers (National Cancer Institute)

What colorectal cancer is not

Colorectal cancers are gastrointestinal cancers that begin in the colon (large intestine) or rectum. They should not be confused with other gastrointestinal cancers such as stomach, liver, pancreas, neuroendocrine, anal or GIST because these cancers can have different symptoms, outlooks, and treatments.

Common types of colorectal cancer

  • Adenocarcinomas – the most common type of colorectal cancers, adenocarcinomas start in cells that make mucus to lubricate the inside of the colon and rectum. 
  • Carcinoid tumors – start from cells in the intestine that produce hormones.
  • Squamous cell cancer – the most common type of anal cancer.


It’s possible that you could have one or more of the following tests (but not all of these will apply to your condition):

  • Imaging (CT scan)
  • Lower endoscopy or colonoscopy
  • Biopsy
  • Physical exam by your medical oncologist
  • Meeting with your surgeon and radiation oncologist


Depending on your unique set of conditions, your treatment could include one or more of the following treatments (but not all of these will apply to your condition):

  • Chemotherapy
  • Radiation
  • Surgery

Your full team of care providers will work closely together to review your diagnostic tests, identify the best course of treatment particular to you, and help you understand your diagnosis and what to expect with any treatment you have.