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The introduction of bowel cancer population screening programs has had a profound impact on gastrointestinal pathology. While the focus is mainly on quality assurance of diagnoses relevant for the outcome of these programs (colorectal cancer and its precursors), incidental findings are increasingly diagnosed. The incidence of such findings is largely unknown. Therefore, we investigated the incidence of incidental findings within the national screening program of the Netherlands. From the Dutch nationwide pathology databank (PALGA), we retrieved all histological diagnoses of patients participating in the national bowel cancer screening program from the start in 2014 until 1/ 1/2021. Descriptive statistics were used. During these 7 years, in total 9407 other polyps and malignancies (262 per 10,000 colonoscopies) were diagnosed. The majority (65%) were classified as inflammatory polyps. The most common malignancies were neuroendocrine tumours (n = 198, 6 per 10,000 colonoscopies); less common were lymphomas (n = 64) and metastases (n = 33). Mesenchymal polyps, such as leiomyomas and lipomas, were relatively common (27 and 16 per 10,000 colonoscopies, respectively), in comparison with neural polyps such as perineuriomas, ganglioneuromas, and neurofibromas (respectively 3, 2, and 1 per 10,000 colonoscopies). This is the largest study into the incidence of nonconventional colorectal polyps and malignancies in a homogeneous cohort of asymptomatic patients. Several of these diagnoses may have consequences for treatment and followup, in particular the malignancies and detection of patients with hereditary cancer syndromes. [ABSTRACT FROM AUTHOR]

Gene fusions involving NTRK1, NTRK2, and NTRK3 are rare drivers of cancer that can be targeted with histology-agnostic inhibitors. This study aimed to determine the nationwide landscape of NTRK/TRK testing in the Netherlands and the usage of pan-TRK immunohistochemistry (IHC) as a preselection tool to detect NTRK fusions. All pathology reports in 2017–2020 containing the search term 'TRK' were retrieved from the Dutch Pathology Registry (PALGA). Patient characteristics, tumor histology, NTRK/TRK testing methods, and reported results were extracted. NTRK/TRK testing was reported for 7457 tumors. Absolute testing rates increased from 815 (2017) to 3380 (2020). Tumors were tested with DNA/RNA-based molecular assay(s) (48%), IHC (47%), or in combination (5%). A total of 69 fusions involving NTRK1 (n = 22), NTRK2 (n = 6) and NTRK3 (n = 41) were identified in tumors from adult (n = 51) and pediatric (n = 18) patients. In patients tested with both IHC and a molecular assay (n = 327, of which 29 NTRK fusion-positive), pan-TRK IHC had a sensitivity of 77% (95% confidence interval (CI), 56–91) and a specificity of 84% (95% CI, 78–88%). These results showed that pan-TRK IHC has a low sensitivity in current routine practice and warrants the introduction of quality guidelines regarding the implementation and interpretation of pan-TRK IHC. [ABSTRACT FROM AUTHOR]

Accurate, consistent and reproducible grading by pathologists is of key‐importance for identification of individual patients with invasive breast cancer (IBC) that will or will not benefit from adjuvant systemic treatment. We studied the laboratory‐specific grading variation using nationwide real‐life data to create insight and awareness in grading variation. Synoptic pathology reports of all IBC resection‐specimens, obtained between 2013 and 2016, were retrieved from the nationwide Dutch Pathology Registry (PALGA). Absolute differences in laboratory‐proportions of Grades I–III were compared to the national reference. Multivariable logistic regression provided laboratory‐specific odds ratios (ORs) for high‐ vs. low‐grade IBC. 33,792 IBC pathology reports of 33,043 patients from 39 laboratories were included, of which 28.1% were reported as Grade I (range between laboratories 16.3–43.3%), 47.6% as Grade II (38.4–57.8%), and 24.3% as Grade III (15.5–34.3%). Based on national guidelines, the indication for adjuvant chemotherapy was dependent on histologic grade in 29.9% of patients. After case‐mix correction, 20 laboratories (51.3%) showed a significantly deviant OR. Significant grading differences were also observed among pathologists within laboratories. In this cohort of 33,043 breast cancer patients, we observed substantial inter‐ and intra‐laboratory variation in histologic grading. It can be anticipated that this has influenced outcome including exposure to unnecessary toxicity, since choice of adjuvant chemotherapy was dependent on grade in nearly a third of patients. Better standardization and training seems warranted. What's new? Histologic grade serves a critical prognostic role in invasive breast cancer (IBC) and is used to guide therapeutic decisions. Evidence indicates, however, that IBC grading varies considerably. Here, grading variation in clinical practice was evaluated using real‐life data from laboratories in the nationwide Dutch Pathology Registry. Laboratories varied in IBC grade I, II, and III reporting. Among grading components, nuclear polymorphism showed the greatest difference between laboratories. Within laboratories, one‐third of pathologists deviated significantly from national proportions for IBC grade I. Despite deployment of uniform guidelines across laboratories, IBC histologic grading is not necessarily performed in a consistent manner. [ABSTRACT FROM AUTHOR]

Aims: Variation in health‐care is undesirable, as this is potentially harmful for patients. In the Netherlands, an e‐learning module was developed to standardise pathological evaluation of colorectal adenomas. We studied the effect of e‐learning on interlaboratory variability in grading of dysplasia in screened conventional colorectal adenomas. Methods and results: A cross‐sectional retrospective study was performed, including all colorectal adenomas from the Dutch population‐based colorectal cancer screening programme, retrieved from the Dutch Pathology Registry (PALGA) from January 2014 to July 2015. The e‐learning tool, commissioned by the National Institute for Public Health, was implemented among screening pathologists from October 2014. Proportions of high‐grade dysplasia (HGD) were compared before (January–July 2014) and after implementation (October 2014–July 2015) of the e‐learning module. Interlaboratory variation was assessed by multilevel mixed‐effects analysis. In total, 20 713 colonoscopies (20 546 patients) were performed after a positive faecal immunochemical screening test, resulting in the inclusion of 56 355 conventional adenomas from 37 pathology laboratories. Before implementation, 12 614 adenomas were diagnosed, including 4.3% with HGD. After implementation, 43 741 adenomas were diagnosed, and the HGD proportion decreased to 3.9%. Univariable analysis showed less deviant proportions of HGD after implementation in 62% of the laboratories (P = 0.019). Multilevel analysis confirmed decreased variation in the risk of diagnosing HGD (P = 0.021). Conclusions: Interlaboratory variability in grading HGD in colorectal adenomas after a positive screening test decreased after implementation of an e‐learning module for pathologists. We therefore conclude that e‐learning has a favourable influence on decreasing diagnostic variability, making this a relevant strategy for health‐care standardisation. [ABSTRACT FROM AUTHOR]

Aims Although high-grade dysplasia ( HGD) is a risk factor for malignant transformation and the future development of adenomas/carcinomas, grade is not incorporated in the Dutch guidelines for colonoscopy surveillance, partly because of presumed interobserver variability. The aim of this study was to analyse, in a nationwide cohort of colorectal adenomas, the interlaboratory variability in the grading of dysplasia in daily practice. Methods and results From the Dutch Pathology Registry, all synoptically reported classic adenomas in The Netherlands in 2013 were identified. The proportion of adenomas with HGD was determined for biopsies and polypectomies, and compared between 37 laboratories by the use of multivariable logistic regression analyses. In total, 21 030 colonoscopies of 20 270 patients were included. HGD was reported in 530 (3.6%) of 14 866 adenomas diagnosed on biopsies (range between laboratories: 0-13.6%) and in 983 (11.8%) of 8346 adenomas diagnosed on polypectomies (range: 3.1-42.9%). After adjustment for case mix, 13 (35%) laboratories reported a significantly lower or higher frequency of HGD than average. Conclusions We observed considerable interlaboratory variation in the grading of dysplasia in colorectal adenomas, which could be only partly explained by differences in case mix. Therefore, better standardization of grading criteria is needed before grade of dysplasia can usefully be incorporated in colonoscopy surveillance guidelines. [ABSTRACT FROM AUTHOR]

Background: HER-2 is a prognostic and predictive marker, but as yet no technique is perfectly able to identify patients likely to benefit from HER-2 targeted therapies. We aimed to prospectively assess the added value of first-line co-testing by IHC, and multiplex ligation-dependent probe amplification (MLPA) and chromogenic in situ hybridization (CISH). Methods: As local validation, HER-2 MLPA and CISH were compared in 99 breast cancers. Next, we reviewed 937 invasive breast cancers, from 4 Dutch pathology laboratories, that were prospectively assessed for HER-2 by IHC and MLPA (and CISH in selected cases). Results: The validation study demonstrated 100% concordance between CISH and MLPA, if both methods were assessable and conclusive (81.8% of cases). Significant variation regarding percentages IHC 0/1+ and 2+ cases was observed between the laboratories (p<0.0001). Overall concordance between IHC and MLPA/CISH was 98.1% (575/586) (Kappa = 0.94). Of the IHC 3+ cases, 6.7% failed to reveal gene amplification, whereas 0.8% of the IHC 0/1+ cases demonstrated gene amplification. Results remained discordant after retrospective review in 3/11 discordant cases. In the remaining 8 cases the original IHC score was incorrect or adapted after repeated IHC staining. Conclusions: MLPA is a low-cost and quantitative high-throughput technique with near perfect concordance with CISH. The use of MLPA in routinely co-testing all breast cancers may reduce HER-2 testing variation between laboratories, may serve as quality control for IHC, will reveal IHC 0/1+ patients with gene amplification, likely responsive to trastuzumab, and identify IHC 3+ cases without gene amplification that may respond less well. [ABSTRACT FROM AUTHOR]

Simple Summary: The presence of an EGFR activating mutation in tumors of non-small-cell lung cancer patients enables effective targeted therapy towards EGFR. Studies that describe a nationwide uptake of EGFR testing, the impact of the switch from single-gene EGFR to multi-gene testing, and the clinical response towards EGFR inhibitors in first-line treatment are limited. From 2013 to 2017 the percentage of patients routinely tested for EGFR mutations increased from 73% to 81% in the Netherlands. A strong shift towards EGFR testing as part of a multi-gene next generation sequencing analysis was observed. However, this did not change the percentage of EGFR mutations that were reported for this patient population, which remained stable at 12%. When treated with EGFR inhibitors that were available in a routine clinical setting prior to 2018, clear differences were observed between the type of EGFR mutation and survival. EGFR mutation analysis in non-small-cell lung cancer (NSCLC) patients is currently standard-of-care. We determined the uptake of EGFR testing, test results and survival of EGFR-mutant NSCLC patients in the Netherlands, with the overall objective to characterize the landscape of clinically actionable EGFR mutations and determine the role and clinical relevance of uncommon and composite EGFR mutations. Non-squamous NSCLC patients diagnosed in 2013, 2015 and 2017 were identified in the Netherlands Cancer Registry (NCR) and matched to the Dutch Pathology Registry (PALGA). Overall, 10,254 patients were included. Between 2013–2017, the uptake of EGFR testing gradually increased from 72.7% to 80.9% (p < 0.001). Multi-gene testing via next-generation sequencing (increased from 7.8% to 78.7% (p < 0.001), but did not affect the number of detected EGFR mutations (n = 925; 11.7%; 95% confidence interval (CI), 11.0–12.4) nor the distribution of variants. For patients treated with first-line EGFR inhibitors (n = 651), exon 19 deletions were associated with longer OS than L858R (HR 1.58; 95% CI, 1.30–1.92; p < 0.001) or uncommon, actionable variants (HR 2.13; 95% CI, 1.60–2.84; p < 0.001). Interestingly, OS for patients with L858R was similar to those with uncommon, actionable variants (HR 1.31; 95% CI, 0.98–1.75; p = 0.069). Our analysis indicates that grouping exon 19 deletions and L858R into one class of 'common' EGFR mutations in a clinical trial may mask the true activity of an EGFR inhibitor towards specific mutations. [ABSTRACT FROM AUTHOR]

Objectives: The recent accelerated FDA approval of sotorasib, a highly selective KRAS G12C inhibitor, offers new opportunities for the treatment of KRAS p.(G12C)-mutated non-squamous non-small cell lung cancer (NSCLC). The objective of the current study was to the determine the prevalence of KRAS mutations in stage IV non-squamous NSCLC in The Netherlands to reveal the potential impact of upcoming KRAS targeted therapy., Materials and Methods: All patients diagnosed with stage IV non-squamous NSCLC in 2013, 2015 and 2017 in the Netherlands were selected by linking the nation-wide Netherlands Cancer Registry (NCR) and the Dutch Pathology Registry (PALGA). Demographic and pathological variables were retrieved from the pathology reports including sex, age, KRAS mutation status, molecular test method used, and the mutation status of other genes., Results: Prevalence for any KRAS mutations in codon 12/13/61/146 was 39.1%. KRAS p.(G12C) was detected in 15.5% of all non-squamous NSCLC cases representing 39.6% of all KRAS-mutant cases. National testing rate for KRAS mutations increased from 70% in 2013 to 82% in 2017. Testing techniques changed significantly over time with next generation sequencing as the main used method in 2017 (71.6%) but did not affect prevalence of KRAS mutations over time. When KRAS was tested as part of a larger panel, the KRAS p.(G12C) mutation was frequently reported with a concurrent mutation in TP53 (47.7%) or STK11 (10.3%)., Conclusion: The high prevalence for KRAS p.(G12C) offers a promising new specific treatment option for 15% of all stage IV non-squamous NSCLC patients., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Objectives: Immunohistochemical expression of programmed death-ligand 1 (PD-L1) is used as a predictive biomarker for prescription of immunotherapy to non-small cell lung cancer (NSCLC) patients. Accurate assessment of PD-L1 expression is therefore crucial. In this study, the extent of interlaboratory variation in PD-L1 positivity in the Netherlands was assessed, using real-world clinical pathology data., Materials and Methods: Data on all NSCLC patients in the Netherlands with a mention of PD-L1 testing in their pathology report from July 2017 to December 2018 were extracted from PALGA, the nationwide network and registry of histo- and cytopathology in the Netherlands. PD-L1 positivity rates were determined for each laboratory that performed PD-L1 testing, with separate analyses for histological and cytological material. Two cutoffs (1% and 50%) were used to determine PD-L1 positivity. Differences between laboratories were assessed using funnel plots with 95% confidence limits around the overall mean., Results: 6,354 patients from 30 laboratories were included in the analysis of histology data. At the 1% cutoff, maximum interlaboratory variation was 39.1% (32.7%-71.8%) and ten laboratories (33.3%) differed significantly from the mean. Using the 50% cutoff, four laboratories (13.3%) differed significantly from the mean and maximum variation was 23.1% (17.2%-40.3%). In the analysis of cytology data, 1,868 patients from 23 laboratories were included. Eight laboratories (34.8%) differed significantly from the mean in the analyses of both cutoffs. Maximum variation was 41.2% (32.2%-73.4%) and 29.2% (14.7%-43.9%) using the 1% and 50% cutoffs, respectively., Conclusion: Considerable interlaboratory variation in PD-L1 positivity was observed. Variation was largest using the 1% cutoff. At the 50% cutoff, analysis of cytology data demonstrated a higher degree of variation than the analysis of histology data., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Accurate, consistent and reproducible grading by pathologists is of key-importance for identification of individual patients with invasive breast cancer (IBC) that will or will not benefit from adjuvant systemic treatment. We studied the laboratory-specific grading variation using nationwide real-life data to create insight and awareness in grading variation. Synoptic pathology reports of all IBC resection-specimens, obtained between 2013 and 2016, were retrieved from the nationwide Dutch Pathology Registry (PALGA). Absolute differences in laboratory-proportions of Grades I-III were compared to the national reference. Multivariable logistic regression provided laboratory-specific odds ratios (ORs) for high- vs. low-grade IBC. 33,792 IBC pathology reports of 33,043 patients from 39 laboratories were included, of which 28.1% were reported as Grade I (range between laboratories 16.3-43.3%), 47.6% as Grade II (38.4-57.8%), and 24.3% as Grade III (15.5-34.3%). Based on national guidelines, the indication for adjuvant chemotherapy was dependent on histologic grade in 29.9% of patients. After case-mix correction, 20 laboratories (51.3%) showed a significantly deviant OR. Significant grading differences were also observed among pathologists within laboratories. In this cohort of 33,043 breast cancer patients, we observed substantial inter- and intra-laboratory variation in histologic grading. It can be anticipated that this has influenced outcome including exposure to unnecessary toxicity, since choice of adjuvant chemotherapy was dependent on grade in nearly a third of patients. Better standardization and training seems warranted., (© 2019 The Authors. International Journal of Cancer published by John Wiley & Sons Ltd on behalf of UICC.)