Lynch syndrome (HNPCC) is caused by germline mutations in mismatch repair (MMR) genes. Which combination of features constitutes the Revised Bethesda Guidelines for testing a CRC tumour for microsatellite instability (MSI)?

• A CRC with family history of breast cancer in a first-degree relative
• B Any CRC regardless of age or family history
• C CRC diagnosed before age 50, or synchronous CRC, or tumour with MSI-H histological features ✓
• D CRC with K-RAS mutation on molecular testing

Explanation

The Revised Bethesda Guidelines (2004) identify criteria for MSI testing of colorectal tumours: CRC diagnosed <50 years; synchronous or metachronous CRC or Lynch-associated tumours; CRC with MSI-H histological features (Crohn's-like lymphocytic reaction, mucinous/signet ring or medullary growth pattern) in a patient <60 years; CRC in ≥1 first-degree relative with Lynch-associated tumour with one cancer diagnosed <50 years; or CRC in ≥2 first/second degree relatives with Lynch-associated tumours regardless of age. Universal tumour testing (MSI/IHC for MMR proteins) in all CRCs is now recommended by many guidelines.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.