biostudies-literatureUnknown9(2)Neumann OIntrahepatic cholangiocarcinoma harbours druggable genetic lesions including FGFR2 gene fusions. Reliable and accurate detection of these fusions is becoming a critical component of the molecular work-up, but real-world data on the performance of fluorescence in situ hybridisation (FISH) and targeted RNA-based next-generation sequencing (NGS) are very limited. Bridging this gap, we report results of the first round robin test for FGFR2 fusions in cholangiocarcinoma and contextualise test data with genomic architecture. A cohort of 10 cholangiocarcinoma (4 fusion positive and 6 fusion negative) was tested by the Institute of Pathology, University Hospital Heidelberg, Germany. Data were validated by four academic pathology departments in Germany. Fusion-positive cases comprised FGFR2::BICC1,The journal of pathology. Clinical research100-107https://www.ebi.ac.uk/biostudies/studies/S-EPMC9896158biostudies-literatureFirst proficiency testing for NGS-based and combined NGS- and FISH-based detection of FGFR2 fusions in intrahepatic cholangiocarcinoma.PMC9896158Lehmann UAlbrecht TIlm KWalker MGoldschmid HWeichert WStenzinger AChristmann JVolckmar ALBartels SSchirmacher PPfarr NNeumann OKirchner MKreipe HTannapfel AKazdal DAllgauer MfalseFirst proficiency testing for NGS-based and combined NGS- and FISH-based detection of FGFR2 fusions in intrahepatic cholangiocarcinoma.Intrahepatic cholangiocarcinoma harbours druggable genetic lesions including FGFR2 gene fusions. Reliable and accurate detection of these fusions is becoming a critical component of the molecular work-up, but real-world data on the performance of fluorescence in situ hybridisation (FISH) and targeted RNA-based next-generation sequencing (NGS) are very limited. Bridging this gap, we report results of the first round robin test for FGFR2 fusions in cholangiocarcinoma and contextualise test data with genomic architecture. A cohort of 10 cholangiocarcinoma (4 fusion positive and 6 fusion negative) was tested by the Institute of Pathology, University Hospital Heidelberg, Germany. Data were validated by four academic pathology departments in Germany. Fusion-positive cases comprised FGFR2::BICC1,2023-01-01T00:00:00Z2023 Mar2026-05-28T11:51:59.036Z2025-04-07T03:22:09.357ZS-EPMC98961583663522510.1002/cjp2.308