AMP case report: A 48-year-old woman with endometrial cancer. Importance of screening for Lynch syndrome in patients with EC

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Discussion
Gynecologic malignancies, especially endometrial cancer, are often the initial cancer diagnosis in women who harbor the germline mutations in the MMR genes associated with Lynch syndrome. Therefore, our awareness needs to be heightened when faced with EC patients. During recent decades, multiple criteria and guidelines have been issued in an attempt to identify patients who warrant screening for LS. The Amsterdam criteria were compiled in 1991 and revised in 1999, advocating the classification of Lynch families based heavily on pedigree patterns coupled with emergence of cancer at a relatively young age. Although addressing the inheritance aspect of Lynch syndrome, these criteria were found to be inadequate as they focused too much on pedigree and excluded those who fell outside of the classical Lynch presentation of CRC at a young age.

Fig. 4. In MSI testing, genomic DNA from a patient’s tumor is compared with genomic DNA from a blood sample. Seven MSI markers are evaluated in this assay (five mononucleotide on the left and two pentanucleotide on the right); the asterisk (*) indicates markers that show instability when comparing the two samples. MSI at two or more of the five mononucleotide markers indicates MSI-H.

Around the same time as the Amsterdam revision, a second set of criteria, the Bethesda guidelines, emerged, also emphasizing pedigree but additionally advocating the use of MSI testing via PCR to evaluate individuals whose presentation is suggestive of a cancer syndrome (such as relatively young age of presentation and synchronous Lynch-associated tumors). According to these guidelines, pedigree was certainly important, but the focus was shifted to the individual and his or her specific presentation, a more effective screening tool for those with a limited family history. Although found to be a much more sensitive mode of screening as compared with the Amsterdam criteria, the Bethesda guidelines still were found to be inadequate, especially for EC patients.

Recently, several organizations including the Association for Molecular Pathology,² the EPICOLON Consortium,³ the National Society of Genetic Counselors and Collaborative Group of the Americas on Inherited Colorectal Cancer,⁴ and EGAPP5 have put forth guidelines that recommend universal screening for all individuals with newly diagnosed CRC using MMR IHC and/or MSI, though no particular algorithm is favored. This approach appears to be cost-effective.^{6, 7}

Table 1. Genetic defect in one of the four MMR proteins (either germline mutation or, in the case of MLH1, somatic promoter hypermethylation also has a gene silencing effect) and the corresponding expected IHC patterns. Because the proteins form dimers, loss of MLH1 is almost always coupled with loss of PMS2, and loss of MSH2 is accompanied by MSH6 loss. Complete loss of expression in the setting of a positive internal control is interpreted as a positive result. The IHC pattern can guide subsequent genetic testing for specific MMR gene sequencing.
*Occasionally, interpretation of IHC can be problematic; some mutations in MLH1 or abnormal methylation may result in false normal MLH1 IHC staining.

The screening guidelines for endometrial cancer are not quite as straightforward. The Society of Gynecologic Oncologists issued recommendations in 2007 for screening patients at risk for LS-associated gynecologic malignancies; however, these again focused on personal/family history and development of cancer before 50 years of age.⁸ However, in one study, based on age alone, six of 10 EC patients would not have been identified using the under 50 years of age criterion for screening.⁹ Also, in comparison to CRC, an increased number of endometrial cancers in LS is due to mutations in MSH6, which tend to develop after age 50. Several institutions are moving to universal screening of EC or using strict criteria based on patient history and tumor histology with MMR IHC.^9,10 Histopathologic features of EC that seem to correlate with LS cases include peritumoral lymphocytes, tumor infiltrating lymphocytes (TILs), presence of tumor heterogeneity, and undifferentiated/dedifferentiated morphologies, lower uterine segment localization, and synchronous ovarian clear cell carcinoma.^10,11

MSI in about 75 percent of endometrial cancer is sporadic, due to MLH1 promoter methylation, which can be identified with a separate methylation-specific PCR assay. In our laboratory we perform MSI analysis using a clinically available kit (Promega Corp., Madison, Wis.) of seven markers—five mononucleotide repeat markers (BAT-25, BAT-26, NR-21, NR-24, and MONO-27) and two pentanucleotide repeat markers (Penta C and Penta D). The mononucleotide markers are used to determine MSI status, and the pentanucleotide markers confirm that the paired samples (normal and tumor) are from the same person. After PCR, amplicons are run on an ABI capillary electrophoresis instrument; tumors showing instability at two or more markers are defined as MSI-H (high), and MSI-L (low) and MSS (stable) tumors have instability at one repeat or no instability, respectively (Fig. 4). Hampel, et al., showed that some Lynch-associated endometrial carcinomas were found to be MSI-L or even MSS, particularly those with MSH6 mutations, lowering the predictive rate of MSI testing. IHC has been shown to be as accurate as MSI and allows for the additional benefit of targeting a specific MMR gene for sequencing based on staining results (Table 1).⁹

Conclusion
This case demonstrates the potential rapidity of events resulting from Lynch syndrome, as the patient went from initial presentation to death in just over one year. Further, this case also shows that while current screening recommendations for LS undergo continuous refinement, testing based on pedigree alone has been proved to be insufficient and should be based on individual case presentations or, as some institutions are adopting, universal screening on all newly diagnosed EC or CRC patients. Finally, this case shows that though there are multiple screening modalities for LS, they are useless unless clinicians think to use them. Thus, it is important to raise awareness of LS in endometrial cancer patients and current screening practices.

References

1. 1. 1. Resnick KE, Hampel H, Fishel R, Cohn DE. Current and emerging trends in Lynch syndrome identification in women with endometrial cancer. Gynecol Oncol. 2009;114(1):128–134.
      2. Funkhouser WK Jr, Lubin IM, Monzon FA, et al. Relevance, pathogenesis, and testing algorithm for mismatch repair-defective colorectal carcinomas: a report of the Association for Molecular Pathology. J Mol Diagn. 2012;14(2):91–103.
      3. Moreira L, Balagner F, Lindor N, et al. Identification of Lynch syndrome among patients with colorectal cancer. JAMA. 2012;208(15):1555–1565.
      4. Weissman SM, Burt R, Church J, et al. Identification of individuals at risk for Lynch syndrome using targeted evaluations and genetic testing: National Society of Genetic Counselors and the Collaborative Group of the Americas on Inherited Colorectal Cancer joint practice guideline. J Genet Couns. 2012;21(4):484–493.
      5. Recommendations from the EGAPP Working Group: genetic testing strategies in newly diagnosed individuals with colorectal cancer aimed at reducing morbidity and mortality from Lynch syndrome in relatives. Genet Med. 2009;11(1):35–41.
      6. Mvundura M, Grosse SD, Hampel H, Palomaki GE. The cost-effectiveness of genetic testing strategies for Lynch syndrome among newly diagnosed patients with colorectal cancer. Genet Med. 2010;12(2):93–104.
      7. Ladabaum U, Wang G, Terdiman J, et al. Strategies to identify the Lynch syndrome among patients with colorectal cancer: a cost-effectiveness analysis. Ann Intern Med. 2011;155(27):69–79.
         8. Lancaster JM, Powell CB, Kauff ND, et al. Society of Gynecologic Oncologists Education Committee statement on risk assessment for inherited gynecologic cancer predispositions. Gynecol Oncol. 2007;107(2):159–162.
      8. Hampel H, Frankel W, Panescu J, et al. Screening for Lynch syndrome (hereditary nonpolyposis colorectal cancer) among endometrial cancer patients. Cancer Res. 2006;66(15):7810–7817.
      9. Garg K, Soslow RA. Lynch syndrome (hereditary non-polyposis colorectal cancer) and endometrial carcinoma. J Clin Pathol. 2009;62(8):679–684.
      10. Garg K, Leitao MM Jr, Kauff ND, et al. Selection of endometrial carcinomas for DNA mismatch repair protein immunohistochemistry using patient age and tumor morphology enhances detection of mismatch repair abnormalities. Am J Surg Pathol. 2009;33(6):925–933.

   Dr. Jenson is a pathology resident, Dr. Tsongalis is director of molecular pathology and professor of pathology, and Dr. Tafe is assistant director of molecular pathology and assistant professor of pathology—all in the Department of Pathology, Dartmouth-Hitchcock Medical Center, Geisel School of Medicine at Dartmouth and Norris Cancer Center, Hanover, NH.

Test yourself: Here are three questions taken from the case report.

Below are three take-home points and questions. Answers to the questions are online now at www.amp.org/casereviews and will be published in CAP TODAY next month.

1. What is the mode of inheritance for Lynch syndrome?
A. X-Linked
B. Mitochondrial
C. Autosomal dominant
D. Autosomal recessive

2. What is the expected IHC pattern associated with a genetic defect in MSH6?
A. MSH6 (+) / MSH2 (−)
B. MSH6 (+) / MSH2 (+)
C. MSH6 (−) / MSH2 (−)
D. MSH6 (−) / MSH2 (+)

3. What is the most common cause of microsatellite instability (MSI) in endometrial carcinoma?
A. MLH1 promoter methylation
B. MLH1 germline mutation
C. MSH6 germline mutation
D. PMS2 germline mutation