Lynch Syndrome (HNPCC) : Mnemonics

Inheritance: Autosomal Dominant (AD)

Cause: Microsatellite instability (MLH1, MSH2 mismatch repair gene mutation)

Types:

1. Lynch 1 syndrome: Early onset colorectal cancers
2. Lynch 2 syndrome: Colorectal cancer + Extraintestinal malignancies (Mnemonic: CEO)
   • Colorectal cancer
   • Endometrial cancer
   • Ovarian cancer

Amsterdam II Criteria for Diagnosis

Mnemonic: 3-2-1-0 rule

1. 3 or more relatives with pathologically verified Lynch cancers
2. 2 or more successive generations
3. 1 or more case diagnosed before 50 years age
4. 0 FAP (Familial Adenomatous Polyposis excluded)

Colorectal cancers: More likely to be mucinous and right-sided

Treatment: Total colectomy with ilio-rectal anastomosis

Annual screening: Age 25 onwards or beginning no later than 5 years before the lowest age of onset in family