Colorectal cancer

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Cancerous tumours of the colon or rectum

A cancerous tumour of the colon or rectum can spread, or metastasize, to other parts of the body. Cancerous tumours are also called malignant tumours.

Adenocarcinoma

Adenocarcinoma is the most common type of colorectal cancer. It makes up more than 95% of all colorectal cancers.

Adenocarcinoma starts in gland cells that line the wall of the colon or rectum (called the mucosa). The gland cells normally make a thick, slippery substance called mucus. Mucus helps stool move through the colon and rectum.

Uncommon subtypes of adenocarcinoma are named based on how they look under a microscope. Mucinous adenocarcinoma is made of cancerous gland cells surrounded by large amounts of mucus. With signet ring cell carcinoma, the nucleus (the part of the cell that has genetic information) in the cancerous gland cells is pushed to one side.

Rare colorectal tumours

The following cancerous tumours of the colon or rectum are rare:

  • small cell carcinoma
  • squamous cell carcinoma, which is treated like anal cancer
  • adenosquamous carcinoma
  • medullary carcinoma
  • neuroendocrine tumours
  • soft tissue sarcoma, such as leiomyosarcoma and gastrointestinal stromal tumour (GIST)
  • non-Hodgkin lymphoma, such as MALT lymphoma
  • melanoma

These rare tumours are usually treated differently than adenocarcinomas, but there are no standard treatments for them. If you have one of these types of cancer, your healthcare team will discuss the treatment options and decide what will work best for you.

Find out more about anal cancer, neuroendocrine tumours, soft tissue sarcoma, gastrointestinal stromal tumours (GISTs), non-Hodgkin lymphoma and melanoma.

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