1. Hereditary Colon Cancer Syndromes
Seth Sweetser, M.D.
Assistant Professor of Medicine
Division of Gastroenterology and Hepatology
Mayo Clinic College of Medicine

2. Objectives Understand the molecular pathways to colon cancer
Recognize the clinical manifestations of the more common hereditary colon cancer syndromes
Differentiate surveillance strategies for individuals with polyposis and oligo-polyposis colorectal cancer syndromes

3. Genetic Instability Pathways That Drive Colon Neoplasias
Shown are the overlapping relationships that define the major pathways of
genomic instability in colon cancers: chromosomal instability, microsatellite
instability caused by defects in DNA mismatch-repair genes that are either
inherited as germ-line defects (e.g., in hereditary nonpolyposis colon
cancer) or somatically acquired (e.g., by aberrant methylation and epigenetic
silencing of MLH1), and the CpG island methylator phenotype.
NEJM 2009:361;25.

4. Hereditary Colon Cancer
Rare
Account for 5% of all colon cancer cases
Diagnostic clues:
Early onset colorectal neoplasia (<50 yo)
Excessive number of colorectal polyps
Multiple primary cancers
Extracolonic benign or malignant tumors
Multiple relatives and/or generations affected
Colon cancer is associated with a family history in up to 25% of cases. As many as 5% are associated with an established hereditary syndrome, demonstrating the profound influence of inheritable genetic mechanisms in the development of this disease. These syndromes confer a diverse spectrum of risk, age of presentation, endoscopic and histological findings, extracolonic manifestations, and modes of inheritance. As the molecular characteristics of these disorders become better described, enhanced genotype-phenotype correlations may offer a more targeted approach to diagnosis, screening, and surveillance. While the strategies for diagnosis and management of familial adenomatous polyposis (FAP) and Lynch syndrome are more established, the approach to newly recognized syndromes such as MUTYH-associated polyposis (MAP) and hyperplastic polyposis syndromes continues to evolve. Effective cancer prevention in affected individuals and at-risk family members first requires timely recognition of these hereditary colon cancer syndromes followed by integration of genetic testing and clinical examinations.
Hereditary colon cancers, in which CRC susceptibility is due to inherited, highly penetrant mutations, may account for approximately 5% of all colon cancer cases.
Recognizing the possibility of familial CRC:
family history of CRC or extracolonic cancers
extracolonic manifestations
age of cancer or polyp diagnosis
histologic features of the polyp or cancer
lifetime polyp burden

5. Hereditary Colon Cancer Syndromes
Autosomal Dominant (50% risk to offspring):
Lynch Syndrome
Familial Adenomatous Polyposis
Peutz-Jeghers Syndrome
Juvenile Polyposis Syndrome
Cowden Syndrome
Autosomal Recessive (25% risk to offspring):
MYH associated polyposis

6. Hereditary Colon Cancer Syndromes
Autosomal Dominant (50% risk to offspring):
Lynch Syndrome
Familial Adenomatous Polyposis
Peutz-Jeghers Syndrome
Juvenile Polyposis Syndrome
Cowden Syndrome
Autosomal Recessive (25% risk to offspring):
MYH associated polyposis

7. Case 1 42-year-old woman is diagnosed with an ascending colon cancer
No prior medical or surgical history other than the uncomplicated births of her two children, ages 5 and 3
Family history: Mother had small bowel cancer at age 74 and maternal uncle had kidney cancer in his sixties
Diagnostic clues to hereditary cancer susceptibility syndrome: Early age onset (<50 yo) and family history with multiple relatives affected.

8. Lynch Syndrome (HNPCC)
Autosomal dominant heritable cancer syndrome
Tendency for right sided or multiple CRC’s, one to few polyps, and extracolonic cancer,
90% of cases caused by defective DNA mismatch repair
Two genes most commonly mutated - MLH1 and MSH2
Improved survival over those with microsatellite stable cancer
…Extracolonic cancer, especially endometrial cancer.

9. Genetic Basis of Lynch Syndrome
The genome contains short, repeated segments of DNA called microsatellites
Prone to mutation during replication
Four DNA mismatch repair genes
MLH1, MSH2, MSH6, PMS2
MMR repair mismatched nucleotide sequences

10. Inactivation of one or two of the DNA mismatch repair (MMR) genes can cause Lynch syndrome
MLH1 and MSH2 are the two DNA MMR genes most frequently mutated
DNA MMR genes can be inactivated in several ways
Germline MMR gene mutations cause 80 to 90% of the cases of Lynch syndrome

11. Does this patient have Lynch Syndrome?
By modified Amsterdam criteria (AC), which includes cancers other than CRC --probably
Modified AC:
3 relatives with a Lynch-associated cancer – one should be first degree relative of the other two (parent, sibling or child)
2 successive generations should be affected
1 should be diagnosed before age 50
Lynch-associated cancer (CRC, cancer of the endometrium, small bowel, ureter or renal pelvis)
Gastroenterology 1999;116:

12. Revised Bethesda Guidelines
Meeting any of the following:
CRC diagnosed under age 50 y of age
Presence of synchronous or metachronous CRC or other Lynch-related tumor regardless of age
CRC in an individual less than 60 y of age, exhibiting tumor infiltrating lymphocytes, Crohn disease-like lymphocytic reaction, mucinous/signet-ring differentiation, or medullary growth pattern
CRC at any age plus CRC or Lynch-related tumor diagnosed before age 50 y in at least 1 first-degree relative
CRC at any age plus CRC or Lynch-related tumor diagnosed in 2 or more first degree or second-degree relatives
Meeting any of the following are sufficient for consideration of MSI testing:
Umar A, et al. J Natl Cancer Inst. 2004;96:

13. Lynch Syndrome: Adenoma Features
Numbers ranging from one to a few
Villous growth pattern
High degree of dysplasia
Probably rapid progression from adenoma to carcinoma

14. Histologic features suggesting MMR mutation
Marked lymphocytic infiltration
Crohn disease-like lymphoid aggregation at tumor margin
Signet ring cell type with mucin production
Medullary growth pattern
Poor differentiation (high grade)
Despite their apparently aggressive histologic characteristics, the overall five year survival rates in affected family members is better than that seen in sporadic colorectal cancer, suggesting that the biology and natural history of Lynch-related tumors is fundamentally different from that of sporadic CRC.
Signet ring cells with mucin production

15. Extracolonic Features of Lynch Syndrome
Café au lait spots
Sebaceous adenocarcinoma
Physical findings in Lynch syndrome are rare – Muir Torre Syndrome
Keratoacanthoma
Sebaceous hyperplasia
Images from Mayo archives, and eMedicine

16. Lynch Syndrome-Related Cancers
Most common extracolonic tumor in Lynch syndrome is endometrial ca.
Cancer risk in Lynch syndrome varies depending on geographic/environmental factors (for example, gastric cancer is a more common Lynch-associated cancer in countries such as China and Korea with a high sporadic prevalence of that disease). Similarly, the age-incidence and spectrum of cancers in Lynch syndrome vary significantly based upon the MMR gene mutated. The frequency of extracolonic malignancies in Lynch syndrome is related to the specific MMR mutation. Some debate of whether prostate or breast cancers might be part of the Lynch syndrome.
Families with MSH6 and possibly PMS2 mutations appear to have an attenuated cancer phenotype (a later age of cancer diagnosis and a lower penetrance) compared to MLH1 and MSH2 families.
Lifetime cancer risk related to Lynch Genotypes:
MSH2 – greater ovarian and upper urologic at approx 10%
MSH6 – greater risk for endometrial at >70%
PMS2 – less CRC risk
Two hallmarks of Lynch Syndrome: 1) early age of onset and 2) multiplicity of cancers
Aarnio, et al - Int J Cancer 1999;81:214-8

17. Lynch-related Turcot Syndrome
Glioblastoma multiforme and colonic polyposis
Earlier age of onset: ages vs years of age in sporadic cases
Better prognosis than sporadic
Distinct from APC mutation related brain tumors: medulloblastoma called Crail’s syndrome
Crails Syndrome is FAP with a brain tumor, specifically meduloblastomas
Hamilton SR, et al., NEJM 1995; 332:

18. Testing for Lynch
Immunohistochemistry(IHC) with MLH1, MSH2 and MSH6, PMS2
Turn-around time same as routine pathology
Can be done on paraffin-embedded tumor tissue
Archival specimen can be used
Microsatellite instability(MSI) on tumor and adjacent normal tissue
Direct sequencing of the MLH1,MSH2, PMS2 and MSH6 genes

19. Microsatellite Instability Testing
Panel of 5 mono and di-nucleotide repeats
>30% with MSI, then tumor MSI(H)
Markers of widespread genomic instability in the microsatellite repeat regions caused because 1 or more the DNA mismatch repair genes are not working
Not necessarily involved in cancer progression A G
The term “microsatellite instability” refers to expansion or contraction of short repetitive DNA sequences (microsatellites) that is due to loss of DNA mismatch repair. Tumors can be tested for microsatellite instability using polymerase chain reaction (PCR) to amplify a standard panel of DNA sequences containing nucleotide repeats. If 30 percent or more of the markers show expansion or contraction of the repetitive sequences in the tumor compared to the normal mucosa from the same patient, the tumor is reported to have a high level of microsatellite instability (MSI-H).
The presence of MSI-H in the tumor tissue suggests that a defect in a DNA mismatch repair gene is present. MSI is highly sensitive for Lynch syndrome; >90% of tumor tissue from patients with Lynch syndrome show high levels of MSI.
Unfortunately, MSI-H status cannot be used alone as a test for Lynch syndrome cancers because the specificity of MSI-H for Lynch syndrome is low. In addition to Lynch colorectal cancers, MSI-H is found in up to 15 percent of sporadic colorectal cancers. In the sporadic group, MSI-H is typically due to loss of normal MMR due to hypermethylation of the promoter region of MLH1, one of the MMR genes. Hypermethylation of the MLH1 promoter leads to epigenetic silencing of the gene.

20. Choosing who to test is crucial
Microsatellite instability and absence of expression of immunostaining can be found without a DNA MMR gene germline mutation
Hypermethylation of the MLH1 promotor accounts for % of sporadic CRC - Not Lynch and not same risk
Generally proximal mucinous, signet ring CRC in older woman without AC or other criteria
Testing is expensive, if IHC and MSI testing are positive, may obligate germline testing
Careful selection of who to test is important
20% to 25% of cases suspected of having a mutation in MSH2 but in which a germline mutation is not detected, can be accounted for by germline deletions in EPCAM/TACSTD1. also suggest the presence of other alterations leading to MSH2 promoter hypermethylation.
The two groups of MSI-H colorectal cancers (sporadic and Lynch-associated MSI-H cancers) can be differentiated by direct measurement of the methylation status of MLH1 in the tumor, or more simply by genetic analysis of the BRAF gene. For reasons that are as yet unclear, activating mutations in BRAF are nearly universal in sporadic MSI-H colorectal cancers but are rare in Lynch cancers. The identification of a BRAF mutation in an MSI-H colorectal cancer essentially rules out Lynch syndrome

21. Sporadic and Lynch-associated MSI-H cancers
Direct measurement of:
Methylation status of MLH1 gene promoter, or
Genetic analysis of the BRAF gene mutation
Activating mutations in BRAF are nearly universal in sporadic MSI-H colorectal cancers but are rare in Lynch cancers
The identification of a BRAF mutation in an MSI-H colorectal cancer essentially rules out Lynch syndrome
most MLH1 deficient tumors are sporadic in origin, and they can be identified if harboring a BRAF V600E mutation or hypermethylation of the MLH1 gene promoter.
Differentiating Sporadic and Lynch-associated MSI-H cancers can be differentiated by:
Direct measurement of the methylation status of MLH1 in the tumor, or more simply by genetic analysis of the BRAF gene. For reasons that are as yet unclear, activating mutations in BRAF are nearly universal in sporadic MSI-H colorectal cancers but are rare in Lynch cancers. The identification of a BRAF mutation in an MSI-H colorectal cancer essentially rules out Lynch syndrome

22. Germline gene testing Mutation IHC for MLH1, MSH2, MSH6, PMS2
Wild type
(non-mutated)
Mutation
hypermethylation
normal
normal
IHC for MLH1,
MSH2, MSH6, PMS2
cancer
cancer
Small DNA base pair damage
cannot be repaired, changes in
microsatellite repeats develop,
DNA base pair mistakes perpetuated
in genes
important to cancer promotion
Able to repair small DNA base pair
mistakes, no microsatellite instability,
no crucial downstream genes that promote
cancer growth are mutated

23. Algorithm for Genetic Testing in patients who fit criteria for Lynch Syndrome
IHC for MLH1,
MSH2, MSH6, PMS2
MSI testing:
panel of 5 markers +
Tumor
Tumor
If positive, formal medical genetics consult
Directed germline gene testing based
on which protein is not expressed on the IHC
Peripheral DNA

24. Consider Genetic Testing for Defective Germline MMR if:
Early onset cancer
Familial clustering of CRC and/or endometrial cancer
Multiple cancers in one person
Right-sided or multiple CRCs with histology showing mucinous, poorly differentiated tumors with increased lymphocytic infiltration

25. Why is knowing if a patient has Lynch syndrome important?
Premise:
CRC risk increases with age
30% of DNA MMR gene carriers will develop CRC by age 40, but by age 75, 90% will have CRC
Screening reduces the rate of CRC in Lynch kindreds
Jarvinen HJ, et al., Gastro 1995; 108:

26. Evolution of Case Recommendations:
Since the actual type of kidney cancer (renal cell or ureter/renal pelvis) was not known, modified AC may or may not be met
Tumor site, young age of onset and mother’s history suggested that patient may have Lynch
IHC for defective DNA mismatch repair performed on tumor tissue before surgery

27. 42 yr old woman is diagnosed with an ascending colon cancer
IHC showed absence of MSH2 on tumor sample prior to surgery
Surgical options discussed
Opts for ileorectostomy, TAH and BSO
Post –op genetics consult
Germline testing verified Lynch syndrome
Predictive genetic testing planned for her children when they reach adolescence

28. Her surveillance and screening plan:
Follow-up with annual endoscopic exam of rectum
Annual urinalysis
Annual skin examination
EGD if family history of gastric cancer

29. Scenario : Her children’s care is affected
For her children, if positive by germline testing then:
Annual colonoscopy beginning age 25 or 5 years younger than youngest CRC in the kindred
Annual endometrial aspiration biopsy and/or transvaginal ultrasound annually beginning at age 35
Annual urine cytology and urinalysis – urine cytology no longer recommended
EGD if family history of gastric cancers
Annual skin examination
Gastroenterology 2001; 121:

30. Recommendations for the proband children if germline testing not done
If no germline testing done then colonoscopy every 1-2 years beginning age 25 until age then annually
Consider similar endometrial cancer screening if Lynch kindred with history of endometrial cancer
Annual urinalysis (not cytology)
EGD if family history of gastric cancers

31. Case 2 55-year-old man undergoes CRC screening.
A colonoscopy reveals twenty adenomatous polyps in the ascending and transverse colon and two sigmoid polyps.
He has a family history of CRC in his father at age 72.
Discussion questions.
What diagnostic and treatment approaches are indicated?
What recommendations should his two sons, ages 20 and 27, receive?
What genetic testing might be considered?

32. Classic FAP Gene: APC (“gate-keeper”) Inheritance: AD
Incidence:1 in 6,000-13,000; ~ 20-25% de novo
Diagnosis: 2nd decade
Major features: > 100 CR adenomas; ~ 100% CRC risk without proctocolectomy
Other cancers: duodenal thyroid, HB
Images from Mayo archives

33. Attenuated FAP <100 polyps Autosomal dominant
Upper GI tract polyps similar to FAP
Right-sided polyps, 70% risk of CRC by age 65
Extreme ends of APC
Point mutations in I1307k are associated with 2 fold risk of CRC in Ashkenazi
Colonoscopy reveals that the large exophytic lesion occupies most of the cecum.

34. Extracolonic Features (FAP)
Duodenal neoplasm
Gastric polyps
Multifocal CHRPEs
Desmoid tumor
Skull osteoma
Images from Mayo archives and eMedicine

35. MYH Polyposis
Another DNA repair pathway causes similar phenotype as FAP or AFAP
Autosomal recessive inheritance associated with germline biallelic mutations in MYH genes
Base excision repair gene involved in correcting oxidative damage: causes the stable guanine adduct to mispair with adenine
Leads to somatic G:C to T:A transversions within the APC gene and inactivation
Typical number of polyps:
MYH stands for Mut Y Human homolog.
MYH encodes a critical member of the DNA base-excision-repair system. Oxidation of DNA leads to the formation of nucleotide mispairs with adenine resulting in somatic G:C to T:A transversions. MYH is an adenine-specific DNA glycosylase that removes mispaired adenines
Cleary SP, et al. Gastro 2009

36. Importance of Biallelic MYH Mutations
Account for 40% of cases in which APC mutation not found
Two most common mutations Y179C and G396D found as compound heterozygote or homozygote
Significance of monoallelic MYH mutation uncertain
Extracolonic cancers occur in 40% (ovarian, bladder, skin cancers)
Like the mismatch repair genes, MYH is a DNA repair gene. Extraintestinal cancers occur in 40% with a spectrum of disease far different than seen in FAP with an increased risk for ovarian, bladder, and skin cancers.

37. Key Characteristic of MYH-Associated Polyposis
Only known autosomal recessive hereditary colon cancer syndrome
Clinical spectrum is variable (Classic – Attenuated – CRC without polyposis)
Screening to establish diagnosis recommended in patients with:
Multiple CR adenomas (>10) who are APC gene mutation negative or
Have apparent autosomal recessive inheritance
Wang L, et al. Gastroenterology 2004
Balaguer F, et al. Clin Gastroenterol Hep 2007

38. Evolution of Case
APC gene testing negative
Underwent genetic testing for two most common MYH mutations (Y179C and G396D)
Homozygous for Y179C mutation -> Biallelic MYH mutation carrier

39. Yearly skin examination
Cancer Surveillance Recommendations for biallelic MYH mutation carriers
Colonoscopy every 1-2 yrs starting at age 18 yrs to remove polyps until polyp burden is great enough that colectomy necessary
Regular EGD with side viewing starting age 25 yrs given risk of duodenal cancer
Yearly skin examination
Similar to attenuated FAP:

40. Conclusion Different molecular pathways to CRC
Lynch syndrome is the most common hereditary colorectal cancer syndrome
Consider with early onset colorectal neoplasia
Multiple primary cancers
Multiple relatives and/or generations affected
Consider MYH polyposis testing when >10 CR adenomas and APC gene testing negative