Mismatch repair protein immunohistochemistry: a useful population screening strategy for Lynch syndrome

Colon cancer: the 2023 Korean clinical practice guidelines for diagnosis and treatment

Colorectal cancer is the third most common cancer in Korea and the third leading cause of death from cancer. Treatment outcomes for colon cancer are steadily improving due to national health screening programs with advances in diagnostic methods, surgical techniques, and therapeutic agents.. The Korea Colon Cancer Multidisciplinary (KCCM) Committee intends to provide professionals who treat colon cancer with the most up-to-date, evidence-based practice guidelines to improve outcomes and help them make decisions that reflect their patients' values and preferences. These guidelines have been established by consensus reached by the KCCM Guideline Committee based on a systematic literature review and evidence synthesis and by considering the national health insurance system in real clinical practice settings. Each recommendation is presented with a recommendation strength and level of evidence based on the consensus of the committee.

Clinicopathological characteristics and loss of mismatch repair protein expression in Chinese upper tract urothelial carcinomas

Expression of DNA mismatch repair (MMR) protein (MLH1, PMS2, MSH2, and MSH6) in upper tract urothelial carcinoma (UTUC) has been explored in Western cohorts, but it is rarely reported in Eastern cohorts. We aimed to assess the loss of MMR protein expression among Chinese UTUC patients and study its clinicopathological implications. We enrolled 175 UTUC patients at our center and tested the expression of MMR proteins by immunohistochemistry. Then, we explored these patients' clinicopathological characteristics. We found loss of MMR proteins in 19 (10.9%) of 175 patients in our cohort (6 MSH2 and MSH6, 2 MSH6 alone, 6 MSH2 alone, 3 MLH1 and PMS2, and 2 PMS2 alone). Loss of MMR proteins was not a significant prognostic factor of relapse-free survival for these patients. In addition, patients with lower T stage or with bladder cancer history were more likely to have loss of MMR protein expression. At last, two metastatic patients (MSH2 and MSH6 loss; MSH2 loss) with loss of MMR protein experienced tumor recession after several cycles of anti-PD-1 immunotherapy. In conclusion, this is the largest Chinese UTUC cohort study to date that explores the loss of MMR protein expression. The rate of MMR loss observed was comparable to that in the Western UTUC cohort, supporting universal UTUC screening in China. Furthermore, a subset of advanced UTUCs with MMR protein loss are probably immunogenic, for whom single or combined immunotherapy may be potential therapeutic options in the future.

Worldwide prevalence of Lynch syndrome in patients with colorectal cancer: Systematic review and meta-analysis

PURPOSE

Lynch syndrome (LS) is the most common hereditary colorectal cancer (CRC) syndrome, with an estimated prevalence of 2% to 3% of CRC. A prevalence study is needed to provide accurate estimates of the true prevalence of LS.

METHODS

MEDLINE (Ovid), Embase, and Web of Science were searched. Prevalence was calculated by random effects meta-analysis models. I² score was used to assess heterogeneity across studies. Meta-regression was performed for between-study variance.

RESULTS

A total of 51 studies were included in this review. The overall pooled yield of LS screening was 2.2% based on all methods of detection. Studies performing germline tests on all participants with CRC reported higher prevalence (5.1%) as opposed to studies only performing germline tests on participants with tumors with mismatch repair deficiency (1.6%) or microsatellite instability (1.1%). Selected cohorts of CRC had a higher prevalence of germline LS diagnoses.

CONCLUSION

LS prevalence across multiple ethnic, geographic, and clinical populations is remarkably similar. Universal germline testing of patients presenting with cancer identifies that most CRCs are attributed to LS. Young patients presenting with CRC and those who fulfill criteria for a familial risk provide the highest returns for LS identification. Our study supports the universal germline CRC screening for LS.

Comparison of universal screening in major lynch-associated tumors: a systematic review of literature

Lynch syndrome (LS) is associated with an increased lifetime risk of several cancers including colorectal (CRC), endometrial (EC), ovarian (OC), urinary (UT) and sebaceous tumors (ST). The benefit for universal screening in CRC and EC is well known. However, this benefit in other major lynch-associated tumors is unclear. We performed a systematic review of all published articles in the MEDLINE database between 2005 to 2017 to identify studies performing universal screening for LS in unselected CRC, EC, OC, UT and ST. All cases with MSI-H (instability in two or more markers) or missing one or more proteins on IHC testing were considered screening positive. Cases with MLH1 promoter hypermethylation or BRAF mutation positive were considered to have somatic mutations. A total of 3788 articles were identified in MEDLINE yielding 129 study arms from 113 studies. The overall pooled yield of universal LS screening and germline mismatch gene mutation was significantly different across the major LS-associated tumors (Mann Whitney test, p < 0.001). The pooled screening yield was highest in ST [52.5% (355/676), 95% CI 48.74-56.26%] followed by EC [22.65% (1142/5041), 95% CI 21.54-23.86%], CRC [11.9% (5649/47,545), 95% CI 11.61-12.19%], OC [11.29% (320/2833), 95% CI 10.13-12.47%] and UT [11.2% (31/276), 95% CI 7.48-14.92%]. ST also had the highest pooled germline positivity for mismatch repair gene mutation [18.8%, 33/176, 95%CI 13.03-24.57], followed by EC [2.6% (97/3765), 95% CI 2.09-3.11], CRC [1.8% (682/37,220), 95% CI 1.66-1.94%], UT [1.8%(3/164), 95% CI - 0.24-3.83%] and OC [0.83%(25/2983), 95% CI 0.48-1.12%]. LS screening in EC yielded significantly higher somatic mutations compared to CRC [pooled percentage 16.94% [(538/3176), 95%CI 15.60-18.20%] vs. 5.23% [(1639/26,152), 95% CI 4.93-5.47%], Mann Whitney test, p < 0.0001. Universal LS testing should be routinely performed in OC, UT and STs in addition to CRC and EC. Our findings also support consideration for IHC and somatic mutation testing before germline testing in EC due to higher prevalence of somatic mutations as well as germline testing in all patients with ST. Our results have implications for future design of LS screening programs and further studies are needed to assess the cost effectiveness and burden on genetic counselling services with expanded universal testing for LS.

Complete Loss of EPCAM Immunoexpression Identifies EPCAM Deletion Carriers in MSH2-Negative Colorectal Neoplasia

Simple Summary

Colorectal carcinomas from patients with Lynch syndrome (LS) due to EPCAM deletions show loss of MSH2 expression. The aim of our study was to evaluate the usefulness of EPCAM expression in identifying carriers of EPCAM deletion among patients with MSH2-negative lesions. MSH2 and EPCAM immunohistochemistry was performed in a large series of lesions (190) composed of malignant and benign neoplasms as well as precursor lesions of different organs from 71 patients with suspected LS due to MSH2 alterations. Germ-line analysis confirmed LS in 68 patients due to MSH2 mutations (53) and EPCAM deletions (15). Among colorectal lesions with lack of MSH2 expression, only 17 were EPCAM-negative and belonged to patients with EPCAM deletions. We confirm that loss of EPCAM expression identifies EPCAM deletion carriers with 100% specificity and we recommend adding EPCAM IHC to the algorithm of MSH2-negative colorectal neoplasia.

Abstract

The use of epithelial cell adhesion molecule (EPCAM) immunohistochemistry (IHC) is not included in the colorectal cancer (CRC) screening algorithm to detect Lynch syndrome (LS) patients. The aim of the present study was to demonstrate that EPCAM IHC is a useful tool to guide the LS germ-line analysis when a loss of MSH2 expression was present. We retrospectively studied MSH2 and EPCAM IHC in a large series of 190 lesions composed of malignant neoplasms (102), precursor lesions of gastrointestinal (71) and extra-gastrointestinal origin (9), and benign neoplasms (8) from different organs of 71 patients suspicious of being LS due to MSH2 alterations. LS was confirmed in 68 patients, 53 with MSH2 mutations and 15 with EPCAM 3′-end deletions. Tissue microarrays were constructed with human normal tissues and their malignant counterparts to assist in the evaluation of EPCAM staining. Among 154 MSH2-negative lesions, 17 were EPCAM-negative, including 10 CRC and 7 colorectal polyps, and 5 of them showed only isolated negative glands. All lesions showing a lack of EPCAM expression belonged to patients with EPCAM 3′-end deletions. EPCAM IHC is a useful screening tool, with 100% specificity to identify LS patients due to EPCAM 3′-end deletions in MSH2-negative CRC and MSH2-negative colorectal polyps.

Worldwide variation in lynch syndrome screening: case for universal screening in low colorectal cancer prevalence areas

To perform a systematic assessment of universal Lynch syndrome (LS) screening yield in colorectal cancer (CRC) patients around the world. Universal screening for LS is recommended in all CRC patients. However, the variation in yield of LS screening in the setting of significant global variation in CRC prevalence is unknown. A systematic review of articles in the MEDLINE database was performed to identify studies performing universal screening for LS. All cases with microsatellite instability (MSI-H) or missing one or more proteins on immunohistochemistry (IHC) were considered screening positive. The overall pooled yield of universal LS screening in 97 study arms from 89 identified studies was 11.9% (5649/47545) and the overall pooled percentage of confirmed LS patients was 1.8% (682/37220). LS screening positivity varied significantly based on geographic region (Kruskal Wallis test, p < 0.001) and reported 5-year CRC prevalence in the country (Fisher's exact, p < 0.001). Significant inverse correlation was found between LS screening positivity and 5-year CRC prevalence (Pearson correlation, r =  - 0.56, p < 0.001). The overall yield of LS screening was 15.00% (382/2553) and rate of confirmed LS was 7.7% (113/1475) in LS screening done in patients ≤ 50 years (16 studies). There is significant geographic variation in LS screening positivity with higher yield in countries with lower prevalence of CRC. Our results highlight the importance of universal LS screening in younger patients and low CRC prevalence countries.

Pancreatic cancer as a sentinel for hereditary cancer predisposition

BACKGROUND

Genes associated with hereditary breast and ovarian cancer (HBOC) and colorectal cancer (CRC) predisposition have been shown to play a role in pancreatic cancer susceptibility. Growing evidence suggests that pancreatic cancer may be useful as a sentinel cancer to identify families that could benefit from HBOC or CRC surveillance, but to date pancreatic cancer is only considered an indication for genetic testing in the context of additional family history.

METHODS

Preliminary data generated at the Huntsman Cancer Hospital (HCH) included variants identified on a custom 34-gene panel or 59-gene panel including both known HBOC and CRC genes for respective sets of 66 and 147 pancreatic cancer cases, unselected for family history. Given the strength of preliminary data and corresponding literature, 61 sequential pancreatic cancer cases underwent a custom 14-gene clinical panel. Sequencing data from HCH pancreatic cancer cases, pancreatic cancer cases of the Cancer Genome Atlas (TCGA), and an unselected pancreatic cancer screen from the Mayo Clinic were combined in a meta-analysis to estimate the proportion of carriers with pathogenic and high probability of pathogenic variants of uncertain significance (HiP-VUS).

RESULTS

Approximately 8.6% of unselected pancreatic cancer cases at the HCH carried a variant with potential HBOC or CRC screening recommendations. A meta-analysis of unselected pancreatic cancer cases revealed that approximately 11.5% carry a pathogenic variant or HiP-VUS.

CONCLUSION

With the inclusion of both HBOC and CRC susceptibility genes in a panel test, unselected pancreatic cancer cases act as a useful sentinel cancer to identify asymptomatic at-risk relatives who could benefit from relevant HBOC and CRC surveillance measures.

Upper tract urothelial carcinomas: frequency of association with mismatch repair protein loss and lynch syndrome

Increased risk for upper tract urothelial carcinoma is described in patients with Lynch syndrome, caused by germline mutations in mismatch repair genes. We aimed to identify the frequency of mismatch repair protein loss in upper tract urothelial carcinoma and its potential for identifying an association with Lynch syndrome. We queried our database to identify upper tract urothelial carcinomas. Patients were cross-referenced for history of colorectal carcinoma or other common Lynch syndrome-associated neoplasms to enrich for potential Lynch syndrome cases. Tumor histopathologic characteristics were reviewed and each case was analyzed for loss of mismatch repair proteins, MLH1, MSH2, MSH6, and PMS2, by immunohistochemistry. Of 444 patients with upper tract urothelial carcinoma, a subset of 215 (encompassing 30 with upper tract urothelial carcinoma and another common Lynch syndrome-associated neoplasm) was analyzed for loss of mismatch repair protein expression. Of 30 patients with Lynch syndrome-associated neoplasms, six had documented Lynch syndrome, including two with Muir-Torre syndrome. Mismatch repair protein loss was identified in 7% of total upper tract urothelial carcinomas and 30% of patients with Lynch syndrome-associated neoplasms (including all patients with Lynch syndrome/Muir-Torre syndrome). Of patients without history of Lynch syndrome-associated neoplasms, 5 of 184 (2.7%) had loss of mismatch repair protein expression. Twelve cases with mismatch repair protein loss demonstrated loss of MSH2 and MSH6, and 2 had isolated loss of MSH6. MLH1 and PMS2 expression were consistently retained. Although increased intratumoral lymphocytes, inverted growth, pushing tumor-stromal interface, and lack of nuclear pleomorphism were more commonly seen in cases with mismatch repair protein loss, only intratumoral lymphocytes and presence of pushing borders were statistically significant. MLH1 and PMS2 testing appear to have little utility in upper tract urothelial carcinoma; however, mismatch repair protein loss of MSH2 and/or MSH6 by immunohistochemistry seems relatively sensitive and specific for identifying patients with potential Lynch syndrome.

Universal Versus Targeted Screening for Lynch Syndrome: Comparing Ascertainment and Costs Based on Clinical Experience

BACKGROUND

Strategies to screen colorectal cancers (CRCs) for Lynch syndrome are evolving rapidly; the optimal strategy remains uncertain.

AIM

We compared targeted versus universal screening of CRCs for Lynch syndrome.

METHODS

In 2010-2011, we employed targeted screening (age < 60 and/or Bethesda criteria). From 2012 to 2014, we screened all CRCs. Immunohistochemistry for the four mismatch repair proteins was done in all cases, followed by other diagnostic studies as indicated. We modeled the diagnostic costs of detecting Lynch syndrome and estimated the 5-year costs of preventing CRC by colonoscopy screening, using a system dynamics model.

RESULTS

Using targeted screening, 51/175 (29 %) cancers fit criteria and were tested by immunohistochemistry; 15/51 (29 %, or 8.6 % of all CRCs) showed suspicious loss of ≥1 mismatch repair protein. Germline mismatch repair gene mutations were found in 4/4 cases sequenced (11 suspected cases did not have germline testing). Using universal screening, 17/292 (5.8 %) screened cancers had abnormal immunohistochemistry suspicious for Lynch syndrome. Germline mismatch repair mutations were found in only 3/10 cases sequenced (7 suspected cases did not have germline testing). The mean cost to identify Lynch syndrome probands was ~$23,333/case for targeted screening and ~$175,916/case for universal screening at our institution. Estimated costs to identify and screen probands and relatives were: targeted, $9798/case and universal, $38,452/case.

CONCLUSIONS

In real-world Lynch syndrome management, incomplete clinical follow-up was the major barrier to do genetic testing. Targeted screening costs 2- to 7.5-fold less than universal and rarely misses Lynch syndrome cases. Future changes in testing costs will likely change the optimal algorithm.

Lower prevalence of Lynch syndrome in colorectal cancer patients in a Japanese hospital-based population

PURPOSE

The aim of this study was to investigate the prevalence of Lynch syndrome among Japanese patients with surgically resected colorectal cancer at a single institution.

METHODS

Of 616 colorectal cancer patients who underwent surgical operation in our institution from January 2005 to August 2010, immunohistochemistry analyses for mismatch repair proteins (MLH1, MSH2, MSH6, and PMS2) and microsatellite instability (MSI) testing for surgically resected, formalin-fixed paraffin-embedded colorectal cancer specimens from 138 colorectal cancer patients under 60 years of age were undertaken. Hypermethylation of the MLH1 promoter and BRAF mutation were analyzed where necessary.

RESULTS

Seven patients were identified as candidates for genetic testing by mismatch repair protein loss (n = 7) or MSI-H (n = 6). Methylation of MLH1 was detected in one case. Three patients were diagnosed with Lynch syndrome, comprising 2.2 % of the total colorectal cancer patients younger than 60 years of age.

CONCLUSION

The prevalence of Lynch syndrome among hospital-based diagnosed cancer patients may therefore be lower than expected in Japan compared with Western populations.

Clinicopathological features and expression of hMLH1 and hMSH2 in Uygur and Han patients with colorectal carcinoma

AIM: To compare the differences in clinicopathological features and expression of hMLH1 and hMSH2 between Uygur and Han patients with colorectal carcinoma.

METHODS: The clinical data for 133 Uygur and 151 Han patients with colorectal carcinoma were analyzed retrospectively. The expression of hMLH1 and hMSH2 proteins was detected in 207 colorectal carcinoma samples, including 98 from Uygur and 109 from Han patients, by immunohistochemical staining.

RESULTS: There were significant differences in onset age, tumor size, pathological differentiation, lymphatic metastasis and tumor stage between the Uygur group and Han group (P < 0.05). In Uygur patients, the loss rate of hMLH1 expression was 9.2% (9/98) in colorectal cancer tissue, and the loss rate of hMSH2 expression was 3.3% (3/98). The loss rate of hMLH1 expression in patients with tumor size > 5 cm was significantly higher than that in patients with tumor size ≤ 5 cm (17.1% vs 3.5%, P < 0.05). The loss rate of hMLH1 expression in patients with lymph node metastasis was 15.1%, significantly higher than that (2.2%) in patients without lymph node metastasis (P < 0.05). The loss rate of hMSH2 in colorectal cancer tissue of Uygur patients (3.1%) was significantly lower than that (10.1%) in Han patients (P < 0.05).

CONCLUSION: There are differences in clinicopathologic features and expression of hMSH2 between Uygur and Han patients with colorectal carcinoma in Xinjiang.

Lynch syndrome screening should be considered for all patients with newly diagnosed endometrial cancer

Lynch syndrome (LS) is an autosomal dominant inherited disorder caused by germline mutations in DNA mismatch repair (MMR) genes. Mutation carriers are at substantially increased risk of developing cancers of the colorectum and endometrium, among others. Given recent recommendations for universal, cost-effective screening of all patients with newly diagnosed colorectal cancer using MMR protein immunohistochemistry, we evaluated MMR protein expression in a series of endometrial cancers in the general population. A total of 605 consecutive cases of primary endometrial cancer at a single institution (1997 to 2013) were evaluated regardless of age, family history, or histologic features. Evaluation methods consisted of immunohistochemistry for the MMR proteins MLH1, MSH2, MSH6, and PMS2, followed by DNA methylation analysis for cases with MLH1/PMS2 deficiency. Germline mutation testing was performed on a subset of cases. Forty MMR-deficient, nonmethylated endometrial cancers were identified: 3 MLH1/PMS2 and 37 MSH6/MSH2 protein deficiencies. Only 25% occurred in women below 50 years of age (range, 39 to 88 y), 1 of which was in a risk-reducing hysterectomy specimen. Only 15% of patients had a prior history of carcinoma, including only 2 patients with prior colorectal carcinoma. Most (80%) of the endometrial cancers were purely endometrioid; there were 2 mixed endometrioid/mucinous, 1 mucinous, 1 serous, 2 clear cell, and 2 carcinosarcoma cases. When grading was applicable, 40% of the endometrial malignancies were FIGO grade 1, 34% grade 2, and 26% grade 3. Thirteen percent arose in the lower uterine segment, and 23% had tumor-infiltrating lymphocytes. Of the tumors with known germline testing, 41% with a LS-associated germline mutation were not associated with any of the traditional indicators that have been recommended for LS screening (ie, age 50 y or younger, personal/family cancer pedigree that meets Bethesda guideline criteria, presence of MMR-associated tumor morphology, or location in the lower uterine segment). These data suggest that a significant number of LS-associated endometrial carcinomas are missed using clinical, histologic, and locational screening parameters and provide support for universal screening of all newly diagnosed endometrial cancers.