Hereditary nonpolyposis colon cancer


Hereditary non-polyposis colorectal cancer (also known as HNPCC, Lynch syndrome, Familial non-polyposis colon cancer) is an inherited genetic condition, which accounts for 2-7% of all colorectal cancers.

HNPCC is divided into two types, type 1 (also known as Lynch syndrome I or familial colon cancer), where tumors localize exclusively in the colon and type 2 (Lynch syndrome II), associated with other cancers of the gastrointestinal or reproductive system (stomach, endometrium, ovary, and urinary tract).



Müller A, Fishel R. Mismatch repair and the hereditary non-polyposis colorectal cancer syndrome (HNPCC). Cancer Invest. 2002;20(1):102-9.

University of California San Francisco (UCSF) Medical Center




Frequently, the patient may be asymptomatic. This is one reason why many organizations recommend periodic screening for the disease. When symptoms do occur, they typically include:

• Change in bowel habits

• Change in the quality or consistency of stools

• Abdominal pain

• Rectal bleeding

• Weakness

• Weight loss

• Loss of appetite

• Feelings of fatigue or weakness.


Symptoms characteristic for HNPCC type 1 also include:

• Stools with mucus

• Black, tarry stool, which may represent bleeding above the rectum.


Symptoms characteristic for HNPCC type 2 include:

• Early presence of colon or rectal polyps



In all organisms mutations and alterations in DNA molecules are normally removed by an internal DNA-repair system. Mutations in the DNA mismatch repair genes (MMR genes) result in accumulation of errors during DNA replication (a process of synthesis of new DNA molecules). This in turn, can lead to abnormal cell functioning, cell death or malignant cell transformation. Mutations in any of the few MMR genes were shown to be connected to HNPCC. Since mutations in MMR genes are present in every cell of the body, cancer can develop in different organs. Uterus, gastrointestinal and urinary system cancers are quite common in people with HNPCC. The exact molecular mechanism of the tumor development in these patients remains poorly understood.

The syndrome is inherited in an autosomal-dominant manner, meaning only one inherited copy of the mutated gene, either from a mother or a father, can cause a disease.



Müller A, Fishel R. Mismatch repair and the hereditary non-polyposis colorectal cancer syndrome (HNPCC). Cancer Invest. 2002;20(1):102-9.



Appropriate check-ups in case of known family predisposition can prevent cancer development.

Screening for women include: yearly pelvic examination, Pap test, and additional tests for ovarian cancer.


Cancer-screening plan may include: 

  • Colon cancer screening
  • Endometrial cancer screening
  • Ovarian cancer screening
  • Urinary system cancer screening
  • Gastrointestinal cancer screening
  • Skin cancer screening.


If you have a family history of colorectal cancer, it is advised to take regular colon examinations by colonoscopy.

Genetic tests for mutations in MMR genes carried out on blood samples are now available.

Microsatellite instability (MSI) – a test on colon tissue, is an alternative method for identifying people who may have inherited the gene mutation for HNPCC. This test is only supportive evidence that someone may have HNPCC. Direct DNA sequencing should be done if MSI is present in tissue.


Source: Cleveland Clinic; National Centre for Medical Genetics




Lynch syndrome significantly increases your chance of developing colon cancer, and often earlier than the general population — before the age of 45.


People with mutations in the MMR genes, either inherited or age-related, are at life-long increased risk of developing colorectal or other aforementioned types of cancers.





Observed colon polyps can be removed before they turn into malignant formation.

If a colorectal cancer is found, it is recommended to remove the colon by a surgery. Surgical options for preventing cancer may also include removal of ovaries and uterus (oophorectomy and hysterectomy) for those women, who are not planning to become pregnant.


Source: Mayo Clinic