Lynch syndrome (HNPCC) colorectal cancer is caused by germline mutations in which group of genes, and what is the characteristic histological feature of these tumors?

• A APC gene; adenomatous polyposis
• B MLH1, MSH2, MSH6, PMS2 mismatch repair genes; microsatellite instability-high (MSI-H) tumors with mucinous/poorly differentiated histology and Crohn's-like lymphocytic reaction ✓
• C SMAD4 gene; signet ring cell carcinoma
• D MUTYH gene; carpet-like polyposis

Explanation

Lynch syndrome results from germline mutations in DNA mismatch repair (MMR) genes — MLH1, MSH2, MSH6, and PMS2 — causing microsatellite instability-high (MSI-H) colorectal cancers. Histologically, these tumors are often mucinous or signet-ring cell, poorly differentiated, located in the right colon, and show a pronounced peritumoral and intratumoral lymphocytic infiltrate (Crohn's-like reaction). MSI-H status confers favorable prognosis and predicts response to immune checkpoint inhibitors. APC mutations cause familial adenomatous polyposis. MUTYH biallelic mutations cause attenuated polyposis.

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.