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Colorectal Cancer Health Center

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Rectal Cancer Treatment (PDQ®): Treatment - Health Professional Information [NCI] - General Information About Rectal Cancer

continued...

Nonpolyposis disorders

  • Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome: mismatch repair (MMR) genes.

Polyposis disorders

Hamartomatous disorders

  • Peutz-Jeghers syndrome: STK11/LKB1 gene.
  • Juvenile polyposis syndrome: SMAD4/DPC4 and BMPR1A genes.
  • Cowden syndrome: PTEN gene.
  • Ruvalcaba-Myhre-Smith syndrome: PTEN gene.
  • Hereditary mixed polyposis syndrome.

HNPCC, the result of defects in MMR genes (involving hMSH2, hMLH1, hPMS1, hPMS2, or hMSH6) represents the most common form of hereditary colorectal cancer, accounting for approximately 3% to 5% of all colorectal malignancies.[8] The majority of genetically defined cases involve hMSH2 on chromosome 2p, and hMLH1 on chromosome 3p. In affected families, 15% to 60% of family members are found to have mutations in hMSH2 or hMLH1; the mutation prevalence depends on features of the family history.[10] Ashkenazi Jews also have an increased risk for colorectal cancer related to a mutation in the APC gene (I1307K), which occurs in 6% to 7% of the Ashkenazi Jewish population.[11]

Other risk factors

More common conditions with an increased risk include:

  • Personal history of colorectal cancer or colorectal adenomas.
  • First-degree family history of colorectal cancer or colorectal adenomas.[12]
  • Personal history of ovarian, endometrial, or breast cancer.[13,14]

These high-risk groups account for only 23% of all colorectal cancers. Limiting screening or early cancer detection to only these high-risk groups would miss the majority of colorectal cancers.[15] (Refer to the PDQ summaries on Colorectal Cancer Screening and Colorectal Cancer Prevention for more information.)

Clinical Presentation and Symptoms

Similar to colon cancer, symptoms of rectal cancer may include the following:[16]

Excepting obstructive symptoms, the symptoms of rectal cancer neither necessarily correlate with the stage of disease nor signify a particular diagnosis.[17] Physical examination may reveal a palpable mass and bright blood in the rectum. With metastatic disease, adenopathy, hepatomegaly, or pulmonary signs may be present.[7] Laboratory examination may reveal iron-deficiency anemia and electrolyte and liver function abnormalities.

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