Celiac disease can be predicted by high levels of anti-tissue transglutaminase antibodies in population-based screening.

OBJECTIVES: The aim of the present study was to evaluate any potential correlation between anti-tissue transglutaminase antibodies of type immunoglobulin A (tTG-IgA) and the degree of gluten-induced enteropathy in children participating in a screening study for celiac disease (CD) and to assess to what extent the revised European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) guidelines cover this group of patients. METHODS: The present study is a substudy of a cross-sectional CD screening study, Exploring the Iceberg of Celiacs in Sweden, a 2-phased study performed during 2005 to 2006 and 2009 to 2010. The 13,279 participating children had a blood test obtained, and those with positive tTG-IgA were recommended a small intestinal biopsy. The tTG-IgA levels at the time of biopsy were compared with those at the assessment of the biopsy. RESULTS: There were 267 children included, of whom 230 were diagnosed as having CD. Of all of the children, 67 children had low tTG-IgA levels (<5 U/mL), of whom 55% had Marsh 3 lesions. All of the children with tTG-IgA levels exceeding 10 times the upper limit of normal values of 5 U/mL, that is, 50 U/mL, were diagnosed as having CD. Lowering the cutoff to 3 U/mL, all but 1 child with 30 U/mL got CD diagnosis. CONCLUSIONS: By adopting the revised ESPGHAN criteria, biopsies could have been omitted in one-fourth of all of the patients. Our results indicate that the criteria may be useful even in screened children. Further studies are needed to confirm whether the 2012 ESPGHAN guidelines should be revised to also apply to the populations being screened.

Efficient and reproducible identification of mismatch repair deficient colon cancer: validation of the MMR index and comparison with other predictive models.

BACKGROUND: The identification of mismatch-repair (MMR) defective colon cancer is clinically relevant for diagnostic, prognostic and potentially also for treatment predictive purposes. Preselection of tumors for MMR analysis can be obtained with predictive models, which need to demonstrate ease of application and favorable reproducibility. METHODS: We validated the MMR index for the identification of prognostically favorable MMR deficient colon cancers and compared performance to 5 other prediction models. In total, 474 colon cancers diagnosed ≥ age 50 were evaluated with correlation between clinicopathologic variables and immunohistochemical MMR protein expression. RESULTS: Female sex, age ≥60 years, proximal tumor location, expanding growth pattern, lack of dirty necrosis, mucinous differentiation and presence of tumor-infiltrating lymphocytes significantly correlated with MMR deficiency. Presence of at least 4 of the MMR index factors identified MMR deficient tumors with 93% sensitivity and 76% specificity and showed favorable reproducibility with a kappa value of 0.88. The MMR index also performed favorably when compared to 5 other predictive models. CONCLUSIONS: The MMR index is easy to apply and efficiently identifies MMR defective colon cancers with high sensitivity and specificity. The model shows stable performance with low inter-observer variability and favorable performance when compared to other MMR predictive models.

Accuracy in celiac disease diagnostics by controlling the small-bowel biopsy process.

OBJECTIVES: In a Swedish celiac disease screening study (Exploring the Iceberg of Celiacs in Sweden), we systematically reviewed the clinical diagnostic procedures with the aim to evaluate the diagnostic accuracy and to take advantage of lessons learned for improving diagnostic routines. MATERIALS AND METHODS: A school-based celiac disease screening study involving 5 Swedish centers, with 10,041 invited 12-year-olds with 7567 consenting participation. All 192 children with elevated serological markers were recommended to undergo small-bowel biopsy, performed and evaluated according to local clinical routines. All of the mucosal specimens were reevaluated by 1 and, when needed, 2 expert pathologists to reach diagnostic consensus. RESULTS: Small-bowel biopsies were performed in 184 children: 130 by endoscopy and 54 by suction capsule. Endoscopic biopsies were inconclusive in 0.6%, compared with 7.4% of biopsies by suction capsule. A patchy enteropathy was found in 9.1%. Reevaluation by the expert pathologist resulted in 6 additional cases with celiac disease and 1 cleared. Sixteen children with normal or inconclusive biopsies, 4 after endoscopy, and 12 after suction capsule were endoscopically rebiopsied, resulting in another 8 cases. The celiac disease prevalence of 30 of 1000 (95% confidence interval 26-34) was not statistically different from that previously reported. CONCLUSIONS: The present review revealed the importance of controlling each step of the diagnostic procedure. Several cases would have been missed by relying only on local routines. To improve the quality of childhood celiac disease diagnostics, we recommend multiple endoscopic biopsies from both proximal and distal duodenum and standardized evaluation by a pathologist with good knowledge of celiac disease.

Mismatch repair defective breast cancer in the hereditary nonpolyposis colorectal cancer syndrome.

Whether or not breast cancer can be a feature of the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome has been debated. In order to clarify if defective mismatch repair (MMR) may indeed play a role in breast cancer, we used the Danish HNPCC register to identify all breast cancers that occurred in MMR gene mutation carriers. In total, 20 female mutation carriers were diagnosed with breast cancer at mean 50 years of age. These tumors were predominantly ductal carcinomas with extensive lymphocytic reactions in 8/14 evaluated tumors. MMR protein immunostaining showed loss of expression of MLH1, MSH2 or MSH6 corresponding to the mutations identified in 7 of the 16 cases investigated, and these tumors were diagnosed at mean 50 (33-66) years of age. The demonstration of defective MMR in a substantial proportion of the breast cancers studied links yet another tumor type to HNPCC. Though the low number do not motivate surveillance, our observation supports a role for defective MMR in breast cancer progression in HNPCC, presumably through accelerated accumulation of mutations in breast cancer-associated genes.

Prognostic impact of array-based genomic profiles in esophageal squamous cell cancer.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is a genetically complex tumor type and a major cause of cancer related mortality. Although distinct genetic alterations have been linked to ESCC development and prognosis, the genetic alterations have not gained clinical applicability. We applied array-based comparative genomic hybridization (aCGH) to obtain a whole genome copy number profile relevant for identifying deranged pathways and clinically applicable markers. METHODS: A 32 k aCGH platform was used for high resolution mapping of copy number changes in 30 stage I-IV ESCC. Potential interdependent alterations and deranged pathways were identified and copy number changes were correlated to stage, differentiation and survival. RESULTS: Copy number alterations affected median 19% of the genome and included recurrent gains of chromosome regions 5p, 7p, 7q, 8q, 10q, 11q, 12p, 14q, 16p, 17p, 19p, 19q, and 20q and losses of 3p, 5q, 8p, 9p and 11q. High-level amplifications were observed in 30 regions and recurrently involved 7p11 (EGFR), 11q13 (MYEOV, CCND1, FGF4, FGF3, PPFIA, FAD, TMEM16A, CTTS and SHANK2) and 11q22 (PDFG). Gain of 7p22.3 predicted nodal metastases and gains of 1p36.32 and 19p13.3 independently predicted poor survival in multivariate analysis. CONCLUSION: aCGH profiling verified genetic complexity in ESCC and herein identified imbalances of multiple central tumorigenic pathways. Distinct gains correlate with clinicopathological variables and independently predict survival, suggesting clinical applicability of genomic profiling in ESCC.

Clinicopathologic factors identify sporadic mismatch repair-defective colon cancers.

Identification of sporadic mismatch repair (MMR)-defective colon cancers is increasingly demanded for decisions on adjuvant therapies. We evaluated clinicopathologic factors for the identification of these prognostically favorable tumors. Histopathologic features in 238 consecutive colon cancers were linked to MMR status based on immunostaining and BRAF mutation status.MMR defects were identified in 22.7% of the tumors, with 46 classified as sporadic. When the clinical parameters of age, sex, and proximal tumor location were combined with the morphologic features with the highest relative risks (RRs), eg, mucinous differentiation (RR, 9.0), tumor-infiltrating lymphocytes (RR, 7.5), absence of necrosis (RR, 7.5), and expanding growth pattern (RR, 5.0) into a 7-factor index, the presence of at least 4 features identified the MMR-defective tumors with 92.3% sensitivity and 75.3% specificity and excluded 61.5% of the tumors from MMR testing. This clinicopathologic index thus successfully selects MMR-defective colon cancers.

Phenotypic heterogeneity in hereditary non-polyposis colorectal cancer: identical germline mutations associated with variable tumour morphology and immunohistochemical expression.

BACKGROUND: Hereditary non-polyposis colorectal cancer (HNPCC) is associated with high risks for colorectal and endometrial cancer, young age at onset and an increased risk of multiple primary tumours. Colorectal cancer in HNPCC is characterised by poor tumour differentiation, an expanding growth pattern, and a pronounced lymphocytic reaction with tumour-infiltrating lymphocytes. AIMS AND METHODS: The mutation spectrum in HNPCC is diverse and in order to clarify whether the HNPCC tumour phenotype is influenced by the underlying genetic alteration, 29 colorectal cancers and 12 adenomas from 24 individuals in two HNPCC families were morphologically and immunohistochemically characterised. RESULTS: The tumour morphology as well as the immunohistochemical expression of beta-catenin varied extensively within the families as well as between synchronous/metachronous colorectal cancers from the same individual. Poor tumour differentiation, an expanding growth pattern, and tumour-infiltrating lymphocytes occurred at higher frequencies in proximal tumours, whereas distal colorectal cancers often lacked distinct HNPCC-associated morphological features. CONCLUSIONS: The clinical, morphological and immunohistochemical variability observed within these families indicates that other mechanisms than the underlying germline mutation influence the HNPCC phenotype. Since morphological features linked to HNPCC are less frequent in distal cancers, it may be particularly relevant to obtain family history and age of onset in these tumours in order to identify individuals with HNPCC.

The added value of PMS2 immunostaining in the diagnosis of hereditary nonpolyposis colorectal cancer.

Identification and characterization of the genetic background in patients with the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome is important since control programmes can in a cost-effective manner prevent cancer development in high-risk individuals. HNPCC is caused by germline mismatch repair (MMR) gene mutations and the genetic analysis of HNPCC therefore includes assessment of microsatellite instability (MSI) and immunohistochemical MMR protein expression in the tumor tissue. MSI is found in >95% of the HNPCC-associated tumors and immunostaining using antibodies against the MMR proteins MLH1, MSH2, and MSH6 has been found to correctly pinpoint the affected gene in about 90% of the cases. The PMS2 antibody was the most recently developed and we have in a clinical material assessed the added value of PMS2 immunostaining in 213 patients with suspected hereditary colorectal cancer. All 119 MSS tumors showed retained expression for all four antibodies and PMS2 did thus not identify any underlying MMR defect in these cases. However, PMS2 immunostaining contributed to the characterization of the MMR defect in a subset of the MSI tumors. Concomitant loss of MLH1 and PMS2, which functionally interact in the MutLalpha complex, was found in 98% of the tumors from patients with germline MLH1 mutations. Among the 12 MSI-high tumors with retained expression of MLH1, MSH2 and MSH6, 8 tumors showed loss of PMS2 staining, and mutations in MLH1 were identified in 2 and mutations in PMS2 in 3 of these individuals. In summary, isolated loss of PMS2 was found in 8% of the MSI-high tumors in our series, including 8/12 previously unexplained MSI-high tumors, in which mutations either in MLH1 or in PMS2 were identified in five cases.

Defective mismatch-repair as a minor tumorigenic pathway in Barrett esophagus-associated adenocarcinoma.

The malignant transformation that characterizes the development of Barrett esophagus-associated adenocarcinomas is a multi-step process in which genetic alterations in various tumor-associated genes accumulate. Defective mismatch repair (MMR) is the cause of microsatellite instability (MSI) pathway that characterizes a subset of gastrointestinal tumors and is specifically associated with tumor development within the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome. The few studies that have assessed MMR defects in Barrett-associated adenocarcinomas have reached different results. We therefore assessed the expression of the MMR proteins MLH1 and MSH2 in a series of 59 Barrett adenocarcinomas and found a loss of MMR protein immunostaining in 2/59 (3%) tumors; one tumor showed a loss of MSH2 expression, the other tumor showed a loss of MLH1, and both tumors displayed an MSI-high phenotype. Our findings suggest that only a small subset of Barrett adenocarcinomas develop because of defective MMR, but demonstrate that MLH1 and MSH2 are the primary targets for defective MMR also in this tumor type.

Predominance of CIN versus MSI in the development of rectal cancer at young age.

BACKGROUND: Development of proximal and distal colorectal cancers involve partly different mechanisms associated with the microsatellite instability (MSI) and the chromosomal instability (CIN) pathways. Colorectal cancers in patients under 50 years of age represent about 5% of the total number of tumors and have been associated with an increased frequency of MSI tumors. However, MSI and CIN may play different roles in the development of colon cancer and rectal cancer, and we have specifically investigated their contribution to the development of rectal cancer at young age. METHODS: Thirty rectal cancers diagnosed before the age of 50 were characterized for DNA-ploidy, MSI, mutations of KRAS and CTNNB1 and immunohistochemical expression of p53, beta-catenin and of the mismatch repair (MMR) proteins MLH1 and MSH2. RESULTS: DNA aneuploidy was detected in 21/30 tumors, KRAS mutations in 6 tumors, no mutations of CTNNB1 were detected but immunohistochemical staining for beta-catenin showed nuclear staining in 6 tumors, and immunohistochemical expression of p53 was detected in 18 tumors. MSI was detected in 3/30 tumors, all of which showed and immunohistochemical loss of staining for the MMR protein MSH2, which strongly indicates a phenotype associated with hereditary nonpolyposis colorectal cancer (HNPCC). CONCLUSIONS: MSI occurs only in a small fraction of the tumors from young patients with rectal cancer, but when present it strongly indicates an underlying HNPCC-causing mutation, and other mechanisms than HNPCC thus cause rectal cancer in the majority of young patients.

Microsatellite instability analysis and/or immunostaining for the diagnosis of hereditary nonpolyposis colorectal cancer?

Hereditary nonpolyposis colorectal cancer (HNPCC) represents 2-4% of colorectal cancers and is caused by a constitutional defect in a mismatch repair (MMR) gene, most commonly affecting the genes MLH1, MSH2, and MSH6. The MMR defect results in an increased cancer risk with the greatest lifetime risks for colorectal cancer and endometrial cancer. The HNPCC-associated tumor phenotype is generally characterized by microsatellite instability (MSI) and immunohistochemical loss of expression of the affected MMR protein. We have evaluated the information obtained from MSI analysis and immunostaining for MLH1, MSH2, and MSH6 in a series of 128 tumors from patients suspected of having HNPCC. A MSI-high pattern was present in 59 of 128 (46%) tumors. Loss of immunohistochemical expression for at least one of these MMR proteins was found in 54 of 59 (92%) evaluable MSI tumors. This loss affected MLH1 in 28, MSH2 in 22, and MSH6 in 21 tumors (with MSH6 as the only loss in 4 tumors). Five (8%) MSI-high tumors showed normal MMR protein expression. All 69 microsatellite stable or MSI-low tumors showed normal immunostaining for all three proteins. In 28 patients, all with MSI-H tumors, germ-line mutations of MLH1, MSH2, or MSH6 had been identified, and a corresponding immunohistochemical loss of MMR protein expression was identified in all these cases. In summary, immunostaining for the MMR proteins MLH1, MSH2, and MSH6 had a sensitivity of 92% and a specificity of 100% for detecting MMR-deficient tumors. MMR protein immunostaining facilitates mutation analysis in suspected HNPCC patients, since it pinpoints the mutated gene, but until the genetic background to the MSI tumors with retained MMR protein expression has been clarified, we suggest that MSI and MMR protein immunostaining should optimally be combined in clinical HNPCC analysis.

Cytogenetic aberrations and heterogeneity of mutations in repeat-containing genes in a colon carcinoma from a patient with hereditary nonpolyposis colorectal cancer.

The majority of tumors from patients affected by hereditary nonpolyposis colorectal cancer (HNPCC) exhibit a mutator phenotype characterized by widespread microsatellite instability (MSI) and somatic mutations in repeated sequences in several cancer-associated genes. An inverse relationship between MSI and chromosomal instability (CIN) has been demonstrated and HNPCC-associated tumors are generally characterized by diploid or near-diploid cells with few or no chromosomal rearrangements. We have studied MSI, somatic mutations in repeat-containing genes, DNA-ploidy, and cytogenetic aberrations in a colon carcinoma from a patient with a germline MLH1 mutation. Mutations in coding repeats were assessed in 10 macroscopically separate areas of the primary tumor and in two lymph nodes. Some of the genes studied (E2F4, MSH3, MSH6, TCF4, and TGFBRII) showed a consistent lack of mutations, whereas others (BAX, Caspase-5 and IGFIIR) displayed alterations in some tumor regions but not in others. The tumor had DNA-index 1.1-1.2 and a stable, aberrant karyotype with extra copies of chromosomes 7 and 12 and the structural aberrations i(1q), der(20)t(8;20), and der(22)t(1;22). The finding of CIN, MSI, and somatic mutations in coding repeats in this tumor suggests that these phenomena may act together in HNPCC tumorigenesis. Furthermore, the observed intratumoral heterogeneity of mutations in coding repeats implies these changes occur late in tumorigenesis and, thus, probably play a role in tumor progression rather than initiation.

Gain of chromosomal region 20q and loss of 18 discriminates between Lynch syndrome and familial colorectal cancer.

Lynch syndrome and familial colorectal cancer type X, FCCTX, represent the two predominant colorectal cancer syndromes. Whereas Lynch syndrome is clinically and genetically well defined, the genetic cause of FCCTX is unknown and genomic differences between Lynch syndrome and FCCTX tumours are largely unknown. We applied array-based comparative genomic hybridisation to 23 colorectal cancers from FCCTX with comparison to 23 Lynch syndrome tumours and to 45 sporadic colorectal cancers. FCCTX tumours showed genomic complexity with frequent gains on chromosomes 20q, 19 and 17 and losses of 18, 8p and 15. Gain of genetic material in two separate regions encompassing, 20q12-13.12 and 20q13.2-13.32, was identified in 65% of the FCCTX tumours. Gain of material on chromosome 20q and loss on chromosome 18 significantly discriminated colorectal cancers associated with FCCTX from Lynch syndrome, which likely signifies different preferred tumourigenic pathways.

Prevalence of childhood celiac disease and changes in infant feeding.

OBJECTIVES: Between 1984 and 1996, Sweden experienced an "epidemic" of clinical celiac disease in children <2 years of age, attributed partly to changes in infant feeding. Whether infant feeding affects disease occurrence and/or the clinical presentation remains unknown. We investigated and compared the total prevalence of celiac disease in 2 birth cohorts of 12-year-olds and related the findings to each cohort's ascertained infant feeding. METHODS: A 2-phase cross-sectional screening study was performed in which 13 279 children from 2 birth cohorts participated: children born during the epidemic (1993) and children born after the epidemic (1997). Previously diagnosed cases were reported and confirmed. Blood samples were analyzed for serological markers and children with positive values were referred for small intestinal biopsy. Infant feeding practices in the cohorts were ascertained via questionnaires. Prevalence comparisons were expressed as prevalence ratios. RESULTS: The total prevalence of celiac disease was 29 in 1000 and 22 in 1000 for the 1993 and 1997 cohorts, respectively. Children born in 1997 had a significantly lower risk of having celiac disease compared with those born in 1993 (prevalence ratio: 0.75; 95% confidence interval: 0.60-0.93; P = .01). The cohorts differed in infant feeding (specifically, in the proportion of infants introduced to dietary gluten in small amounts during ongoing breastfeeding). CONCLUSIONS: A significantly reduced prevalence of celiac disease in 12-year-olds indicates an option for disease prevention. Our findings suggest that the present infant feeding recommendation to gradually introduce gluten-containing foods from 4 months of age, preferably during ongoing breastfeeding, is favorable.

Interobserver variability in the evaluation of mismatch repair protein immunostaining.

Immunohistochemical staining for mismatch repair proteins has during recent years been established as a routine analysis in many pathology laboratories with the aim to identify tumors linked to the hereditary nonpolyposis colorectal cancer syndrome. Despite widespread application, data on reliability are lacking. We therefore evaluated interobserver variability among 6 pathologists, 3 experienced gastrointestinal pathologists and 3 residents. In total, 225 immunohistochemically stained colorectal cancers were evaluated as having normal, weak, loss of, or nonevaluable mismatch repair protein staining. Full consensus was achieved in 51% of the stainings for MLH1, 61% for PMS2, 83% for MSH2, and 45% for MSH6. Weak stainings were the main cause of reduced consensus, whereas contradictory evaluations with normal as well as loss of staining were reported in 2% to 6% of the tumors. Interobserver variability was considerable, though experienced pathologists and residents reached the same level of consensus. Because results from immunohistochemical mismatch repair protein stainings are used for decisions on mutation analysis and as an aid in the interpretation of gene variants of unknown significance in hereditary nonpolyposis colorectal cancer, the interobserver variability identified highlights the need for quality assessment programs, including guidelines for classification of different expression patterns.

Lynch syndrome (hereditary nonpolyposis colorectal cancer) diagnostics.

BACKGROUND: Preventive programs for individuals who have high lifetime risks of colorectal cancer may reduce disease morbidity and mortality. Thus, it is important to identify the factors that are associated with hereditary colorectal cancer and to monitor the effects of tailored surveillance. In particular, patients with Lynch syndrome, hereditary nonpolyposis colorectal cancer (HNPCC), have an increased risk to develop colorectal cancer at an early age. The syndrome is explained by germline mutations in DNA mismatch repair (MMR) genes, and there is a need for diagnostic tools to preselect patients for genetic testing to diagnose those with HNPCC. METHODS: Patients (n = 112) from 285 families who were counseled between 1990 and 2005 at a clinic for patients at high risk for HNPCC were selected for screening to detect mutations in MMR genes MLH1, MSH2, MSH6, and PMS2 based on family history, microsatellite instability (MSI), and immunohistochemical analysis of MMR protein expression. Tumors were also screened for BRAF V600E mutations; patients with the mutation were considered as non-HNPCC. RESULTS: Among the 112 patients who were selected for screening, 69 had germline MMR mutations (58 pathogenic and 11 of unknown biologic relevance). Sixteen of the 69 mutations (23%) were missense mutations. Among patients with MSI-positive tumors, pathogenic MMR mutations were found in 38 of 43 (88%) of patients in families who met Amsterdam criteria and in 13 of 22 (59%) of patients in families who did not. Among patients with MSI-negative tumors, pathogenic MMR mutations were found in 5 of 17 (29%) of families meeting Amsterdam criteria and in 1 of 30 (3%) of non-Amsterdam families with one patient younger than age 50 years. In three patients with MSI-negative tumors who had pathogenic mutations in MLH1 or MSH6, immunohistochemistry showed loss of the mutated protein. CONCLUSION: Our findings suggest that missense MMR gene mutations are common in HNPCC and that germline MMR mutations are also found in patients with MSI-negative tumors.

The contribution of the hereditary nonpolyposis colorectal cancer syndrome to the development of ovarian cancer.

OBJECTIVE: Ovarian cancer has one of the highest fractions of hereditary cases. The hereditary breast and ovarian cancer syndrome, primarily due to mutations in BRCA1 and BRCA2, is the main cause of heredity, but also the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome confers an increased risk of ovarian cancer. In order to clarify the contribution of HNPCC to the development of ovarian cancer, we collected data on family history of cancer and characterized MMR function in a consecutive series of 128 tumors unselected for age at diagnosis and previously characterized for BRCA gene mutations. METHODS: Expression of the MMR proteins MLH1, PMS2, MSH2, and MSH6 was analyzed by immunohistochemistry using tissue microarray sections. Tumors with reduced staining or loss of staining were also analyzed for microsatellite instability (MSI). RESULTS: Loss of MMR protein expression was identified in 3 ovarian cancers, all of which had a MSI-high phenotype. DNA sequence analysis revealed disease-causing germline mutations (deletions of exons 4-6 in MLH1 and a 1-nucleotide deletion in exon 5 of MSH6) in two patients diagnosed at ages 40 and 49 years, both of whom had family histories suggestive of HNPCC. The genetic defect in the third case, which was a 47-year old woman without knowledge about her family history with loss of MLH1/PMS2 expression in the tumor tissue, remains elusive. A family history suggestive of HNPCC was identified in an additional case, but this tumor showed normal, retained MMR protein expression and a microsatellite stable phenotype. CONCLUSIONS: About 2% of ovarian cancer is caused by germline mutations in the MMR-genes, a minor proportion as compared to the contribution of the BRCA-genes (11% in the present series). However, identification of HNPCC patients is important since it allows inclusion of high-risk individuals into control programs aimed at preventing the more frequent colorectal and endometrial cancers. Tumors within the HNPCC-spectrum should therefore be included when recording a family history of cancer among patients diagnosed with ovarian cancer.

Loss of mismatch repair protein immunostaining in colorectal adenomas from patients with hereditary nonpolyposis colorectal cancer.

Colorectal adenomas occur at younger age, at increased frequency and have a greater tendency for malignant transformation in patients with hereditary nonpolyposis colorectal cancer (HNPCC). We performed immunostaining for the mismatch repair proteins MLH1, PMS2, MSH2 and MSH6 in 35 colorectal adenomas from 26 patients with HNPCC and identified loss of immunostaining in 23/35 (0.66) adenomas. Loss of mismatch repair protein immunostaining was particularly frequent in large (>5 mm) (14/16) and proximally located (13/15) adenomas, whereas the gene mutated--MLH1 or MSH2--and the type of mutation did not seem to affect the results. We conclude that loss of mismatch repair protein immunostaining is detected at a lower rate in adenomas than in carcinomas associated with HNPCC. Adenomatous tissue can thus be used for immunostaining of mismatch repair proteins in clinical investigations of HNPCC, but whereas loss of immunostaining may pinpoint the gene affected and thereby guide mutation analysis, retained staining cannot exclude that the adenoma developed as part of the syndrome due to reduced sensitivity. However, the analysis has a greater chance of being informative if large and proximally located adenomas are selected.

Microsatellite instability and expression of MLH1 and MSH2 in carcinomas of the small intestine.

BACKGROUND: Carcinomas of the small intestine are rare, but the risk is greatly increased in patients with hereditary nonpolyposis colorectal cancer (HNPCC) due to an inherited mismatch repair (MMR) gene mutation, most commonly affecting the genes MLH1 or MSH2. Defective MMR is characterized by microsatellite instability (MSI) and loss of MMR protein expression in the tumor tissue. However, a subset of several sporadic tumor types, including about 15% of colon cancers, also evolve through defective MMR. METHODS: The authors have assessed the frequency of MSI and analyzed the immunohistochemical expression of MLH1 and MSH2 in a population-based series of 89 adenocarcinomas of the small intestine. To study the contribution of MSI and defective MMR protein expression in young patients, 43 cancers of the small intestine from patients below age 60 years (including 24 tumors from the population-based series and an additional 19 tumors from young individuals) were also analyzed. RESULTS: MSI was detected in 16/89 tumors (18%) in the population-based series, and immunohistochemistry revealed loss of expression for MLH1 in 7/16 MSI tumors and in 2/73 MSS tumors, whereas all tumors showed normal expression for MSH2. Among the young patients, the authors identified MSI in 10/43 tumors (23%), and 6 of these 10 MSI tumors showed immunohistochemical loss of MMR protein expression, which affected MLH1 in 3 cases and MSH2 in 3 cases. CONCLUSIONS: The frequency of MSI (18%) in adenocarcinomas of the small intestine equals that of colon cancer. However, silencing of MLH1 seems to explain the MSI status in only about half of the MSI tumors. Among patients with cancer of the small intestine before age 60 years, MSI is found in 23% of the cases, with MLH1 and MSH2 being affected at equal frequencies, indicating that HNPCC may underly a subset of such cases.