Rectal Cancer Diagnosis

Rectal cancers are often found after symptoms appear. But most people with early rectal cancer don’t have symptoms, which usually only develop with more advanced disease. This is why we recommend regular screening tests to detect the disease at an early stage when it’s easier to treat.

If you have symptoms that suggest you may have rectal cancer, your doctor will take your medical history, perform a physical examination, and likely order diagnostic tests.

If we suspect you may have rectal cancer based on those results, our specialists will do a colonoscopy and take a biopsy. In this test, the doctor removes a small piece of tissue with a special instrument. One of our expert pathologists (doctors who specialize in diagnosing disease) then examines the tissue sample under a microscope.

Genetic Testing

Rectal cancers can involve a number of different genetic mutations that cause normal cells to become cancerous. These changes in the genes, called somatic mutations, are found only in cancer cells. They are not found in your normal cells and they can’t be passed down to your children.

For some advanced cancers, pathologists at Memorial Sloan Kettering will do molecular testing on the tumor to find somatic mutations. These mutations can show certain behaviors of the tumor and predict how it might react to certain treatments. Knowing as much as possible about the tumor’s genetic makeup can help your treatment team choose a plan of care that’s most likely to help you.

If you have metastatic disease, your doctor will test biopsy samples for mutations in genes called EGFRKRAS, and BRAF, which are common in rectal cancer, as well as mutations in other less common genes.