Revised Bethesda Guidelines (MSI Testing)
The REVISED BETHESDA GUIDELINES (Umar and colleagues 2004) identify colorectal tumors that should be TESTED for MICROSATELLITE INSTABILITY.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Colorectal cancer diagnosed under age 50
- No
- Synchronous or metachronous colorectal or other Lynch-associated tumors…
- No
- Colorectal cancer with MSI-high HISTOLOGY diagnosed under age 60
- No
- Colorectal cancer in a patient with ONE OR MORE FIRST-DEGREE relatives with a…
- No
- Colorectal cancer in a patient with TWO OR MORE FIRST- OR SECOND-DEGREE…
- Yes
Result: MSI testing indicated
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Criterion 1
- Colorectal cancer under 50.
- Criterion 2
- Synchronous or metachronous Lynch-associated tumors, REGARDLESS OF AGE.
- Criterion 3
- MSI-high HISTOLOGY under 60 - a pathologist’s judgment, not a lab result. The 60 was settled by a VOTE.
- Criterion 4
- One or more FIRST-degree relatives with a Lynch tumor, one cancer under 50.
- Criterion 5
- Two or more FIRST- OR SECOND-degree relatives, REGARDLESS OF AGE. Note the different degree from criterion 4.
- Spectrum
- FAR BROADER than Amsterdam II: adds stomach, ovarian, pancreas, biliary tract, brain, sebaceous lesions.
- Disagreement
- A gastric-and-ovarian family FAILS Amsterdam II on spectrum alone and STILL triggers Bethesda. The two tools will disagree, correctly.
- Ages
- THREE different age rules across five criteria, and two have none. Do not carry one threshold across the set.
- Scope
- Decides WHO GETS A TEST, not who has Lynch syndrome. Failing all five does NOT exclude it.
What you enter
- Colorectal cancer diagnosed under age 50.
- Synchronous or metachronous colorectal or other Lynch-associated tumors, REGARDLESS OF AGE.
- Colorectal cancer with MSI-high HISTOLOGY diagnosed under age 60.
- Colorectal cancer in a patient with ONE OR MORE FIRST-DEGREE relatives with a Lynch-associated tumor, one of the cancers diagnosed under age 50.
- Colorectal cancer in a patient with TWO OR MORE FIRST- OR SECOND-DEGREE relatives with Lynch-associated tumors, REGARDLESS OF AGE.
Full field descriptions
- Colorectal cancer diagnosed under age 50. AGE RULE: under 50. Any one criterion alone indicates testing.
- Synchronous or metachronous colorectal or other Lynch-associated tumors, REGARDLESS OF AGE. AGE RULE: none. Any one criterion alone indicates testing.
- Colorectal cancer with MSI-high HISTOLOGY diagnosed under age 60. AGE RULE: under 60. Any one criterion alone indicates testing.
- Colorectal cancer in a patient with ONE OR MORE FIRST-DEGREE relatives with a Lynch-associated tumor, one of the cancers diagnosed under age 50. AGE RULE: one cancer under 50. Any one criterion alone indicates testing.
- Colorectal cancer in a patient with TWO OR MORE FIRST- OR SECOND-DEGREE relatives with Lynch-associated tumors, REGARDLESS OF AGE. AGE RULE: none. Any one criterion alone indicates testing.
How this is calculated
- Rule
- ANY ONE of five criteria indicates MSI testing. The OPPOSITE of Amsterdam II, which needs ALL SIX.
Umar A, Boland CR, Terdiman JP, et al. Revised Bethesda guidelines for hereditary nonpolyposis colorectal cancer (Lynch syndrome) and microsatellite instability. J Natl Cancer Inst. 2004;96(4):261-268. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.