Immunohistochemistry is not an accurate first step towards the molecular diagnosis of MUTYH-associated polyposis.

Identifying patients with germline MUTYH mutation-associated polyposis is presently difficult. The aim of this study is to investigate the possibilities of IHC as a screening test to select patients for MUTYH mutation analysis. The expression of MUTYH protein in colorectal adenomas or cancer was studied by IHC using three different (1 polyclonal and 2 monoclonal) antibodies in six samples from patients with biallelic MUTYH mutations, in three samples from patients with a single MUTYH mutation, and in 11 samples from patients without MUTYH mutations. With the polyclonal antibody, adenomas and carcinomas from patients with biallelic MUTYH mutations showed a strong supranuclear cytoplasmic staining without epithelial nuclear staining. The strong supranuclear staining was also observed in the three samples from patients with a single MUTYH mutation and in nine out of 11 samples from patients without MUTYH mutations, with or without nuclear staining. Samples incubated with the monoclonal antibodies showed a non-specific pattern. Our results demonstrate that, in contrast with previous data, the cytoplasmic staining in neoplastic cells does not discriminate MUTYH mutated from unmutated cases. At present, IHC cannot be used in clinical practice to differentiate between colorectal tissue with and without germline MUTYH mutations.

Compound heterozygosity for two MSH2 mutations suggests mild consequences of the initiation codon variant c.1A>G of MSH2.

Mono-allelic germline mutations in mismatch repair (MMR) genes lead to Lynch syndrome, an autosomal dominant syndrome with an increased risk of predominantly colorectal and endometrial cancers. Bi-allelic germline mutations in MMR genes predispose to haematological malignancies, brain tumours, gastrointestinal tumours, polyposis and features of neurofibromatosis type 1 in early childhood.We report a brother and a sister with bi-allelic germline mutations in MSH2; a pathogenic deletion of the first 6 exons and a variant of the initiation codon (c.1A>G (p.Met1?)), whereas their phenotypes (four colorectal cancers, small bowel carcinoma and 15 adenomas at age 39 and 48, and colorectal cancer, endometrial cancer and four adenomas at age 33 and 44, respectively) are more suggestive of a mono-allelic pathogenic MMR gene mutation. The carcinomas showed microsatellite instability in the presence of MLH1, PMS2, MSH2 and MSH6 proteins, indicating that the variant c.1A>G leads to an alternative protein with reduced activity that is retained in the tumours.Our data suggest that the MSH2 variant c.1A>G (p.Met1?) should not be considered as a regular pathogenic mutation that leads to a strongly increased cancer risk, though it possibly contributes to a more severe phenotype when combined with a truncating mutation on the other allele.

Interpretation of immunohistochemistry for mismatch repair proteins is only reliable in a specialized setting.

We examined the validity of immunohistochemistry for mismatch repair (MMR) proteins in colorectal cancer specimens to identify patients at risk for Lynch syndrome (hereditary nonpolyposis colorectal cancer) and patients with sporadic microsatellite instable colorectal cancer. This was assessed by observer agreement for and accuracy of interpretation of immunohistochemistry. Seven pathologists from 5 different pathology laboratories evaluated 100 molecularly defined colorectal cancers stained for MLH1, PMS2, MSH2, and MSH6. Two of the pathologists were experienced in interpretation of immunohistochemistry for MMR proteins. After evaluation of a subset of 20 cases, a discussion meeting was organized, after which pathologists evaluated all 100 cases. Staining patterns were interpreted as aberrant, normal, or indefinite. In 82% of tumors, 5 or more pathologists reached the same interpretation, which was considered the consensus diagnosis. Consensus was reached slightly less frequently in microsatellite instable than in stable tumors, and interobserver variation was moderate to substantial (kappa: 0.49-0.79). More microsatellite instable tumors showed an indefinite staining pattern compared with microsatellite stable tumors. Three out of 7 pathologists, including the 2 experienced pathologists, did not miss a microsatellite instable tumor. Each pathologist found at least 1 tumor with an aberrant staining pattern, whereas consensus was a normal staining pattern and the tumor was microsatellite stable. We conclude that, if restricted to experienced pathologists, immunohistochemistry is a valid tool to identify patients at risk for Lynch syndrome and patients with sporadic microsatellite instable colorectal cancer. An indefinite or aberrant staining result has to be followed by molecular microsatellite instability analysis to confirm the presence of a defective DNA MMR system.

Most patients with colorectal tumors at young age do not visit a cancer genetics clinic.

PURPOSE: This study examined the referral process for genetic counseling at a cancer genetics clinic in patients with colorectal cancer and to search for determinants of variation in this referral process. METHODS: Patients who were recently diagnosed with colorectal cancer at a young age or multiple cancers associated with Lynch syndrome, hereditary nonpolyposis colorectal cancer, (N = 119) were selected from PALGA, the nationwide network and registry of histopathology and cytopathology in the Netherlands. In a retrospective analysis, we examined whether these patients visited a cancer genetics clinic and identified determinants for referral to such a clinic. Factors of patients, professional practice, and hospital setting were explored with logistic regression modeling. RESULTS: Thirty-six (30 percent) patients visited a cancer genetics clinic. Seventy percent of patients whom the surgeon referred to a cancer genetics clinic decided to visit such a clinic. Analysis of determinants showed that patients with whom the surgeon discussed referral and that were treated in a teaching hospital were more likely to visit a cancer genetics clinic. CONCLUSION: The referral process is not optimally carried out. To deliver optimal care for patients suspected of hereditary colorectal cancer, this process must be improved with interventions focusing on patient referral by surgeons and raising awareness in nonteaching hospitals.

The prognostic significance of the intra-follicular tumor cell proliferative rate in follicular lymphoma.

BACKGROUND AND OBJECTIVES: In follicular lymphoma histological grading is used to predict clinical behavior and to stratify patients for treatment. However, the reproducibility of histological grading is poor and the clinical significance of the difference between grade 1 and grade 2 follicular lymphoma is unclear. Data on proliferation characteristics with respect to prognosis in follicular lymphoma are inconsistent. DESIGN AND METHODS: We assessed the Proliferation Index in follicles, using Mib-1 immunohistochemical staining in lymph node biopsies from 51 patients with follicular lymphoma who were receiving uniform first-line treatment consisting of cyclophosphamide, vincristine, prednisone and interferon alpha2b. RESULTS: The median Proliferation Index was 16.9 (range 3.1-49.2). In grades 1 and 2 follicular lymphoma (n=45) it was 16.1, compared to 24.2 in grade 3 (n=6; p=0.02). At a median follow-up of 71 months, patients with a Proliferation Index below the median had a significantly prolonged time to progression (median not reached vs. 15 months for those with a Proliferation Index above the median; p=0.0006) and improved overall survival (median not reached vs. 42 months, respectively; p=0.002). In multivariate analysis, the Proliferation Index retained its predictive value. Additional prognostic information was especially provided in patients with a low International Prognostic Index. Histological grade did not predict outcome. INTERPRETATION AND CONCLUSIONS: The Proliferation Index is a biological marker that is strongly and independently predictive for outcome in follicular lymphoma, as shown even in this relatively small series of patients. It is easily applicable and reproducible and therefore superior to histological grading in identifying clinically aggressive follicular lymphoma, requiring other types of treatment.

Unfavorable pathological characteristics in familial colorectal cancer with low-level microsatellite instability.

A high degree of microsatellite instability (MSI) in colorectal cancer (CRC) is a hallmark of hereditary non-polyposis colorectal cancer (HNPCC), caused by germline defects in the mismatch repair (MMR) genes. A low degree of instability (less than 30% of the microsatellites) is seen in a subset of tumors. To clarify the significance of this low degree of MSI phenotype, we studied the differences between patients with colorectal tumors with high-level, low-level and no MSI. Colorectal tumors with no (n = 68) and low-level (n = 18) MSI of patients clinically suspected of HNPCC were compared to colorectal tumors with high-level MSI (n = 12) of patients that carry a pathogenic germline mutation in a MMR gene. Compared to tumors with no MSI, tumors with low-level MSI were classified more frequently as stage T3 or T4 (100% vs 68% respectively), and showed less immune response (P = 0.02). No significant differences in familial CRC risk were found by comparing pedigrees of these two groups of tumors. Compared to the group of tumors with high-level MSI, the group of tumors with low-level MSI had a less suspicious family history, a higher percentage of lymph node metastasis (56 vs 17%), and less immune response. Thus, with respect to genetic risks, familial CRC can be divided into two groups: Tumors with high-level MSI and tumors with low-level or no MSI. However, tumors with low-level MSI show unfavorable pathological characteristics compared to tumors with no and tumors with high-level MSI. These differences suggest a distinct underlying biology of CRC with low-level MSI.

Increased vascularization predicts favorable outcome in follicular lymphoma.

PURPOSE: In malignant lymphoma, angiogenesis has been associated with adverse outcome or more aggressive clinical behavior. This correlation has been established in groups of patients with a large heterogeneity regarding lymphoma subtypes and treatment regimens. The aim of this study is to investigate the significance of vascularization in patients with follicular lymphoma receiving uniform first-line treatment. EXPERIMENTAL DESIGN: We assessed microvessel density (MVD) in pretreatment lymph node biopsies of 46 previously untreated patients with follicular lymphoma using anti-CD34 immunohistochemical staining and interactive quantification. In a selection of cases, vascular endothelial growth factor (VEGF)-RNA in situ hybridization was done. Patients were treated with cyclophosphamide-vincristine-prednisone induction chemotherapy combined with IFN-alpha2b. Thirty-six patients responded and received IFN-alpha as maintenance therapy. RESULTS: MVD ranged from 10 to 70 per measurement field of 0.19 mm2 (median, 38). Median progression-free survival was 47 months in patients with MVD in the highest tertile and only 13 months in patients with lower MVD. Overall survival in patients with low vessel density was 59 months. In patients with high vessel density, median overall survival was not reached. Multivariate analysis indicated that MVD was independently associated with overall survival. There was a lack of correlation between VEGF-RNA expression and vessel density. CONCLUSION: This study shows that in follicular lymphoma increased vascularization is associated with improved clinical outcome. Furthermore, VEGF-A expression seems not to be involved in follicular lymphoma angiogenesis.

Allelic imbalance in the diagnosis of benign, atypical and malignant Spitz tumours.

To test the diagnostic usefulness of allelic imbalance (AI) analysis based on routinely paraffin-embedded tissue, a series of 55 benign Spitz naevi, Spitz tumours with uncertain malignant potential, and malignant Spitzoid melanomas was investigated. Laser microdissection was used to ensure representative sampling of lesional cells and to investigate AI in separate tumour areas of four melanomas. AI was found in 2/12 (17%) typical Spitz naevi, 3/9 (33%) atypical Spitz tumours, 12/17 (65%) atypical Spitz tumours suspicious for melanoma and 15/17 (88%) Spitzoid melanomas. Additional immunohistochemical staining for Ki-67 using the MIB-1 antibody revealed positive deeply situated lesional cells in 0/6 (0%) Spitz naevi, 1/8 (13%) atypical Spitz tumours, 5/14 (35%) atypical Spitz tumours suspicious for melanoma, and 7/14 (50%) Spitzoid melanomas, respectively. Two of the melanomas examined for AI in separate tumour areas showed intratumoural genetic heterogeneity. In view of the finding of AI and deeply situated Ki-67 positive cells not only in melanomas but also in Spitz tumours with uncertain malignant potential, these approaches appear to have no direct diagnostic applicability for the distinction between benign and malignant Spitz tumours. Further molecular studies will be required to determine whether Spitz tumours and Spitzoid melanomas are unrelated entities, or whether there is a true spectrum of tumour progression.