In families at risk for hereditary non-polyposis colorectal cancer (HNPCC) that do not fulfill all clinical criteria for HNPCC, additional evidence is sought by testing cancer specimens for microsatellite instability (MSI). We investigated whether the location of a colorectal cancer (CRC) predicts the result of MSI-testing in these families. One hundred and seven patients suspected for HNPCC were offered MSI-testing. MSI-testing was positive in 6/7 patients with endometrial carcinoma and in 22/100 patients with CRC. Only one out of 22 (4%) rectal cancers was MSI-positive, and in this patient no mismatch repair (MMR) gene mutation was found. Right-sided colon carcinomas were more likely to be MSI-positive (14/37 or 38%), followed by left-sided colon carcinomas (7/4 or 17%) (p < 0.05), with 6/14 and 4/7 MMR gene mutations, respectively. The likelihood that a tumor would be MSI-positive was 3.3 times greater for right-sided than for left-sided colon cancer (OR 3.3, p < 0.05). Microsatellite instability was 8.1 times more frequent in colon cancers than in rectal cancers (p < 0.05). The presence of MSI was independently related to fulfillment of the Bethesda criteria (OR 7.0, p = 0.01). In families with multiple cases of colorectal cancer, the rectal cancers are only rarely MSI-positive. This indicates that even in families with multiple colorectal cancers, rectal cancers are most commonly of sporadic origin.

Biomarker analysis for colorectal cancer has been shown to be reliable in Europe with 97% of samples tested by EQA participants to be correctly classified. This study focuses on errors during the annual EQA assessment. The aim was to explore the causes and actions related to the observed errors and to provide feedback and assess any improvement between 2016 and 2017. An electronic survey was sent to all laboratories with minimum one genotyping error or technical failure on ten tumor samples. A workshop was organized based on 2016 survey responses. Improvement of performance in 2017 was assessed for returning participants ( n = 76), survey respondents ( n = 13) and workshop participants ( n = 4). Survey respondents and workshop participants improved in terms of (maximum) analysis score, successful participation, and genotyping errors compared to all returning participants. In 2016, mostly pre- and post-analytical errors (both 25%) were observed caused by unsuitability of the tumor tissue for molecular analysis. In 2017, most errors were due to analytical problems (50.0%) caused by methodological problems. The most common actions taken ( n = 58) were protocol revisions (34.5%) and staff training (15.5%). In 24.1% of issues identified no action was performed. Corrective actions were linked to an improved performance, especially if performed by the pathologist. Although biomarker testing has improved over time, error occurrence at different phases stresses the need for quality improvement throughout the test process. Participation to quality improvement projects and a close collaboration with the pathologist can have a positive influence on performance. Electronic supplementary material The online version of this article (10.1007/s00428-019-02525-9) contains supplementary material, which is available to authorized users.

BackgroundMalignant lymphomas are classified based on morphology, immunophenotype, genetics and clinical features. The pathological diagnosis is generally considered difficult and prone to mistakes. Since non-random chromosomal translocations are specifically involved in specific entities, their detection is an important adjunct for increasing the reliability of the diagnosis. Recently, split-signal fluorescence in situ hybridization has become available as a robust method to detect chromosomal breaks in paraffin-embedded formalin-fixed tissues. A bright field approach would bring this technology within the reach of every pathology laboratory. Design and MethodsOur study was initiated to determine the consistency between chromogenic in situ hybridization and fluorescence in situ hybridization, both using split-signal probes developed for the detection of chromosomal breaks. Five hundred and forty cases of 11 lymphoma entities and reactive, benign lymphoid tissues, collected from eight different pathology laboratories, placed on 15 fluorescence in situ hybridization pre-stained tissue microarray slides, were double stained for the chromogenic hybridization. For each core morphology and actual signal were compared to the original fluorescence hybridization results. In addition, hematoxylin background staining intensity and signal intensity of the double-staining chromogenic in situ hybridization procedure were analyzed. ResultsWith respect to the presence or absence of chromosomal breaks, 97% concordance was found between the results of the two techniques. Hematoxylin background staining intensity and signal intensity were found to correspond. The overall morphology after doublestaining chromogenic in situ hybridization had decreased compared to the initial morphology scored after split-signal fluorescence in situ hybridization staining. ConclusionsWe conclude that double-staining chromogenic in situ hybridization is equally reliable as fluorescence in situ hybridization in detecting chromosomal breaks in lymphoid tissue. Although differences in morphology, hematoxylin staining and chromogenic signal intensity vary between the tumor entities none of the entities appeared more easy or difficult to score.Key words: double staining, CISH, split-signal, lymphoma diagnostics.Citation: van Rijk A, Svenstroup-Poulsen T, Jones M, Cabeçadas J, Cigudosa JC, Leoncini L, Mottok A, Bergman CC, Pouliou E, Hamilton Dutoit S, and van Krieken HJ. Double-staining chromogenic in situ hybridization as a useful alternative to split-signal fluorescence in situ hybridization in lymphoma diagnostics. Haematologica. 2010;95:247-252.