**4. Identifying patients at risk for Lynch syndrome**

In 1991, the International Collaborative Group on Hereditary Nonpolyposis Colorectal Cancer established research criteria, which became known as the Amsterdam Criteria (AC I), for the diagnosis of LS (Vasen et al., 1991). These criteria were broadened in 1999 as the Amsterdam Criteria II (AC II) to recognize a diagnostic role for extra-colonic tumors and suggested that LS-associated cancers should be suspected in relatives (Vasen et al., 1999) (see Table 1).


Table 1. Amsterdam Criteria I and II.

Assays to detect methylation of the *MLH1* promoter that can recognize epigenetic mechanisms that lead to MSI-H, should be considered along with IHC for MMR gene testing (Whelan et al., 2002). For example, studies have shown that methylation of the small proximal region in the *MLH1* promoter located -248 to -178 relative to the gene transcription start site invariably correlates with loss of *MLH1* expression (Kang et al., 2002). If methylation is present, the patient most likely has sporadic tumor rather than LS-associated

IHC has been shown to be a convenient and readily performed test for the detection of germline MMR gene mutations. There are, however, studies of mutations in the MMR genes that are not detected by IHC (Vasen et al., 2004). In fact, by most reports, there is an approximate 5-10 % false negative rate with both IHC and MSI. That is, up to 90-95% of CRCs and ECs seen in LS patients are MSI-H or lack at least one MMR protein product on IHC testing (Ferreira et al., 2009). Therefore, most experts recommend that IHC and MSI testing in combination, along with family and personal history, be used to maximize identification of patients at risk for LS so that germline genetic testing may confirm the

In 1991, the International Collaborative Group on Hereditary Nonpolyposis Colorectal Cancer established research criteria, which became known as the Amsterdam Criteria (AC I), for the diagnosis of LS (Vasen et al., 1991). These criteria were broadened in 1999 as the Amsterdam Criteria II (AC II) to recognize a diagnostic role for extra-colonic tumors and suggested that LS-associated cancers should be suspected in relatives (Vasen et al., 1999)

**At least 3 relatives with histologically verified colorectal cancer (CRC):** 

**At least 3 relatives must have a cancer associated with Lynch Syndrome (CRC, EC, stomach, ovary, ureter, renal pelvis, brain, small bowel, hepato-**

**At least 1 of the LS-associated cancers diagnosed at <50 years of age;** 

**At least 1 of the with CRC diagnosed at <50 years of age; Familial adenomatous polyposis (FAP) should be excluded.** 

**One is a first-degree relative of the other 2; At least 2 successive generations affected;** 

**One is a first-degree relative of the other 2; At least 2 successive generations affected** 

**FAP should be excluded in any CRC cases; Tumors should be verified whenever possible.** 

**4. Identifying patients at risk for Lynch syndrome** 

carcinoma.

diagnosis.

(see Table 1).

AC I

**AC II** 

**biliary, sebaceous tumors):** 

(adapted from Vasen et al., 1991 & Vasen et al., 1999).

Table 1. Amsterdam Criteria I and II.

Individuals meeting the AC I were presumptively defined as having LS. However, once MSI analyses and genetic testing became available, it became clear that certain families who met AC II criteria did not have an identifiable MMR germline mutation (Lindor et al., 2005). In fact, approximately half of patients with LS will be missed by these criteria and approximately half will meet the criteria and not have LS ie., do not carry MSI or MMR variations; but a high familial risk of uncertain etiology. The term "familial colorectal cancer type X" has been suggested for these patients to distinguish them from those with LS (Lindor et al., 2005).

As a result of this major limitation of the AC, the Bethesda Guidelines were originally developed (1997) and revised (2004) to help identify patients with CRC or other LSassociated cancers who should be screened for MSI (Umar et al., 2004). If found to have microsatellite unstable cancers, these patients should undergo subsequent germline MMR genetic testing (see Table 2).

#### **Tumors from individuals should be tested for MSI if:**

**CRC1 diagnosed in a patient who is <50 years of age;** 

**Presence of synchronous, or metachronous LS-associated tumors2, regardless of age; CRC with MSI-H histology3 diagnosed in a patient who is <60 years of age; CRC diagnosed in a patient with 1 or more first-degree relatives with an LSassociated cancer2, with one of the cancers being diagnosed under 50 years of age; CRC diagnosed in a patient with 2 or more first- or second-degree relatives with LS-associated cancers2 regardless of age.** 

(adapted from Umar et al., 2004 and NCCN Guidelines Version 2.2011).

1 Endometrial cancer <50 years of age is not included in the guidelines, however, current evidence suggests that these individuals should be evaluated for LS.

2 LS-associated cancers include: CRC, EC, stomach, ovarian, ureter/renal pelvis, pancreas, hepatobiliary tract, brain (glioblastomas as seen in Turcot syndrome), small bowel, sebaceous adenomas and keratoacanthomas (seen in Muir-Torre syndrome).

3 Presence of tumor infiltrating lymphocytes, Crohn's-like lymphocytic reaction, mucinous (signet-ring) differentiation, or medullary growth pattern.

Table 2. Revised Bethesda Guidelines.

Despite the revised Bethesda criteria, multiple studies show the guidelines have low specificity, with approximately 80% of individuals who meet the criteria will not have LS (Hampel et al., 2005, 2006). Concerns that both the AC and Bethesda guidelines may miss a substantial portion of patients with LS, most investigators agree that all CRC cases be screened for MSI and that any case identified as MSI-H and/or show absence of ≥1 MMR protein, undergo further genetic testing for LS (EGAPP recommendations, 2009). Further, even with normal MSI and IHC, it is important to consider both the patient and their family history when determining to proceed with germline testing for LS.

While it appears that these guidelines focus on CRC patients, it is important to know that they are at high risk of developing a synchronous or metachronous cancers, especially of the colon, rectum, endometrium and/or ovary (Lu et al., 2005; Lynch et al., 1977; Mecklin & Jarvinen, 1986; Watson et al., 2001). An early study found that among 33 families with "cancer family syndrome", the risk of a second LS-associated cancer was approximately 30% within 10 years of the initial cancer diagnosis and up to 50% within 15 years of the initial cancer diagnosis (Mecklin & Jarvinen, 1986). Another report found the annual metachronous CRC rates to be 2.1% and 1.7% between *MLH1* and *MSH2* families, respectively, as compared to 0.33% for the general population (Lin et al., 1998). In a study by Lu et al., dual primary cancers (CRC and gynecologic-endometrial or ovarian) were reported in 16 women (14%) of 117 women with LS (Lu et al, 2005). An earlier study found synchronous and metachronous cancers: endometrial (21 patients), CRC (28 patients), and either gastric, small bowel, or urinary tract cancers (6 patients), in 80 women with LS-associated ovarian cancer (Watson et al., 2001).

The Society of Gynecologic Oncologists Education Committee published guidelines to identify women with a personal or family history of EC or ovarian cancer, and synchronous or metachronous CRC, whom may benefit from genetic risk assessment for LS (Lancaster et al., 2007) (see Table 3).


(adapted from Lancaster et al., 2007).

\* LS-associated cancers include: CRC, EC, stomach, ovarian, ureter/renal pelvis, pancreas, hepatobiliary tract, brain (glioblastomas as seen in Turcot syndrome), small bowel, sebaceous adenomas and keratoacanthomas (seen in Muir-Torre syndrome).

Table 3. Society of Gynecologic Oncologist: Guidelines for Lynch Syndrome Risk Assessment.
