BackgroundImmunohistochemical staining for mismatch repair proteins is efficient and widely used to identify mismatch repair defective tumors. The tumors typically show uniform and widespread loss of MMR protein staining. We identified and characterized colorectal cancers with alternative, heterogenous mismatch repair protein staining in order to delineate expression patterns and underlying mechanisms.MethodsHeterogenous staining patterns that affected at least one of the mismatch repair proteins MLH1, PMS2, MSH2 and MSH6 were identified in 14 colorectal cancers. Based on alternative expression patterns macro-dissected and micro-dissected tumor areas were separately analyzed for microsatellite instability and MLH1 promoter methylation.ResultsHeterogenous retained/lost mismatch repair protein expression could be classified as intraglandular (within or in-between glandular formations), clonal (in whole glands or groups of glands) and compartmental (in larger tumor areas/compartments or in between different tumor blocks). These patterns coexisted in 9/14 tumors and in the majority of the tumors correlated with differences in microsatellite instability/MLH1 methylation status.ConclusionsHeterogenous mismatch repair status can be demonstrated in colorectal cancer. Though rare, attention to this phenomenon is recommended since it corresponds to differences in mismatch repair status that are relevant for correct classification.Virtual SlidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1771940323126788

Background As pathogenic variants in the gene for RBM20 appear with a frequency of 6% among Danish patients with dilated cardiomyopathy (DCM), it was the aim to investigate the associated disease expression in affected families. Methods and Results Clinical investigations were routinely performed in DCM index-patients and their relatives. In addition, ≥76 recognized and likely DCM-genes were investigated. DNA-sequence-variants within RBM20 were considered suitable for genetic testing when they fulfilled the criteria of (1) being pathogenic according to the American College of Medical Genetics and Genomics-classification, (2) appeared with an allele frequency of <1:10.000, and (3) segregated with DCM in ≥7 affected individuals. A total of 80 individuals from 15 families carried 5 different pathogenic RBM20 -variants considered suitable for genetic testing. The penetrance was 66% (53/80) and age-dependent. Males were both significantly younger and had lower ejection fraction at diagnosis than females (age, 29±11 versus 48±12 years; P <0.01; ejection fraction, 29±13% versus 38±9%; P <0.01). Furthermore, 11 of 31 affected males needed a cardiac transplant while none of 22 affected females required this treatment ( P <0.001). Thirty percent of RBM20 -carriers with DCM died suddenly or experienced severe ventricular arrhythmias although no adverse events were identified among healthy RBM20 -carriers with a normal cardiac investigation. The event-free survival of male RBM20 -carriers was significantly shorter compared with female carriers ( P <0.001). Conclusions The disease expression associated with pathogenic RBM20 -variants was severe especially in males. The findings of the current study suggested that close clinical follow-up of RBM20 -carriers is important which may ensure early detection of disease development and thereby improve management.

IntroductionTelomere shortening is associated with a number of common age-related diseases. A role of telomere shortening in osteoarthritis (OA) has been suggested, mainly based on the assessment of mean telomere length in ex vivo expanded chondrocytes. We addressed this role directly in vivo by using a newly developed assay, which measures specifically the load of ultra-short single telomeres (below 1,500 base pairs), that is, the telomere subpopulation believed to promote cellular senescence.MethodsSamples were obtained from human OA knees at two distances from the central lesion site. Each sample was split into three: one was used for quantification of ultra-short single telomeres through the Universal single telomere length assay (STELA), one for histological Mankin grading of OA, and one for mean telomere length measurement through quantitative fluorescence in situ hybridization (Q-FISH) as well as for assessment of senescence through quantification of senescence-associated heterochromatin foci (SAHF).ResultsThe load of ultra-short telomeres as well as mean telomere length was significantly associated with proximity to lesions, OA severity, and senescence level. The degree of significance was higher when assessed through load of ultra-short telomeres per cell compared with mean telomere length.ConclusionsThese in vivo data, especially the quantification of ultra-short telomeres, stress a role of telomere shortening in human OA.

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