Lynch syndrome (hereditary nonpolyposis colorectal cancer) is caused by germline mutations in DNA mismatch repair genes (MLH1, MSH2, MSH6, PMS2). The molecular hallmark that develops in tumors arising in these patients is:

• A Chromosomal instability with aneuploidy
• B Microsatellite instability ✓
• C Philadelphia chromosome formation
• D Oncometabolite accumulation

Explanation

Defective mismatch repair leads to accumulation of errors in repetitive DNA sequences called microsatellites, producing microsatellite instability (MSI). This is the hallmark of Lynch syndrome tumors. Option A describes the pathway seen in familial adenomatous polyposis (APC mutations). Option C is specific to CML. Option D describes IDH-mutated gliomas and AML.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.