Hereditary nonpolyposis colorectal cancer (HNPCC) usually occurs in patients younger than age 45 and can result in the development of cancers in a variety of tissues, such as the colon, rectum, endometrium, stomach, ovaries, brain, and skin. A major genetic characteristic of HNPCC tumors is microsatellite instability (MSI). Microsatellites are short repeated sequences of DNA, and MSI results when mutations in genes that are responsible for repairing damaged DNA cause microsatellites to become longer or shorter. Cancers that exhibit MSI account for about 15% of all colorectal cancers.
Because HNPCC results from inherited mutations, it is possible that family members of patients with HNPCC also have the genetic characteristics that put them at an increased risk for cancers associated with a particular mutation. In 1997, a panel of experts created the Bethesda Guidelines, which outlined criteria for testing tumors from patients with colorectal cancer for MSI so scientists can better understand the development process of HNPCC and identify patients with the syndrome. Such testing would also allow affected family members to take measures to reduce their risk of developing HNPCC-associated cancers.
In a commentary, Asad Umar, D.V.M., Ph.D., of the National Cancer Institute, and colleagues summarize a meeting in 2002 at which experts looked at the most recent evidence about HNPCC gene mutations and revised the Bethesda Guidelines for testing colorectal tumors for MSI. The revised criteria suggest that tumors from patients with colorectal cancer should be tested f
Contact: Katherine Arnold
Journal of the National Cancer Institute