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Genetics of Breast and Gynecologic Cancers (PDQ®)

Clinical Management of Other Hereditary Breast and/or Gynecologic Cancer Syndromes

Lynch syndrome

As mismatch repair genes were identified as the genetic basis of Lynch syndrome, microsatellite instability was identified as a common molecular marker of mismatch repair deficiency. Approximately 15% of sporadic colorectal cancers show microsatellite instability, while up to 28% of sporadic endometrial cancers have this molecular change.[1,2] Most frequently, sporadic tumors with microsatellite instability have hypermethylation of the MLH1 promoter. In Lynch syndrome–related tumors showing microsatellite instability, there is typically loss of one or more of the proteins associated with the mismatch repair genes.

Certain histopathologic features are also strongly suggestive of a microsatellite instability phenotype, including the presence of tumor infiltrating lymphocytes, peritumoral lymphocytes, undifferentiated carcinomas, and lower uterine segment tumors. Use of clinical criteria is one strategy of selection criteria for tumor testing. Computer models have also been used to predict the probability of a mismatch repair gene mutation and can be used in the absence of microsatellite instability or immunohistochemistry information.[3-6] Overall, however, there is a move towards universal testing of colorectal and endometrial tumors when tumor tissue is available. (Refer to the Diagnostic strategies for all individuals diagnosed with colorectal cancer [universal testing] section in the PDQ summary on Genetics of Colorectal Cancer for more information.)


  1. Vilar E, Gruber SB: Microsatellite instability in colorectal cancer-the stable evidence. Nat Rev Clin Oncol 7 (3): 153-62, 2010. [PUBMED Abstract]
  2. Nakamura A, Osonoi T, Terauchi Y: Relationship between urinary sodium excretion and pioglitazone-induced edema. J Diabetes Investig 1 (5): 208-11, 2010. [PUBMED Abstract]
  3. Balmaña J, Stockwell DH, Steyerberg EW, et al.: Prediction of MLH1 and MSH2 mutations in Lynch syndrome. JAMA 296 (12): 1469-78, 2006. [PUBMED Abstract]
  4. Barnetson RA, Tenesa A, Farrington SM, et al.: Identification and survival of carriers of mutations in DNA mismatch-repair genes in colon cancer. N Engl J Med 354 (26): 2751-63, 2006. [PUBMED Abstract]
  5. Kastrinos F, Allen JI, Stockwell DH, et al.: Development and validation of a colon cancer risk assessment tool for patients undergoing colonoscopy. Am J Gastroenterol 104 (6): 1508-18, 2009. [PUBMED Abstract]
  6. Khan O, Blanco A, Conrad P, et al.: Performance of Lynch syndrome predictive models in a multi-center US referral population. Am J Gastroenterol 106 (10): 1822-7; quiz 1828, 2011. [PUBMED Abstract]
  • Updated: April 3, 2015