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AimsGene fusions assays are key for personalised treatments of advanced human cancers. Their implementation on cytological material requires a preliminary validation that may make use of cell line slides mimicking cytological samples. In this international multi-institutional study, gene fusion reference standards were developed and validated.MethodsCell lines harbouringEML4(13)–ALK(20) andSLC34A2(4)–ROS1(32) gene fusions were adopted to prepare reference standards. Eight laboratories (five adopting amplicon-based and three hybridisation-based platforms) received, at different dilution points two sets of slides (slide A 50.0%, slide B 25.0%, slide C 12.5% and slide D wild type) stained by Papanicolaou (Pap) and May Grunwald Giemsa (MGG). Analysis was carried out on a total of 64 slides.ResultsFour (50.0%) out of eight laboratories reported results on all slides and dilution points. While 12 (37.5%) out of 32 MGG slides were inadequate, 27 (84.4%) out of 32 Pap slides produced libraries adequate for variant calling. The laboratories using hybridisation-based platforms showed the highest rate of inadequate results (13/24 slides, 54.2%). Conversely, only 10.0% (4/40 slides) of inadequate results were reported by laboratories adopting amplicon-based platforms.ConclusionsReference standards in cytological format yield better results when Pap staining and processed by amplicon-based assays. Further investigation is required to optimise these standards for MGG stained cells and for hybridisation-based approaches.

Cholesterol granulomas are common in the mastoid antrum and air cells of the temporal bone. In the paranasal sinuses, especially in the frontal sinus, they have occasionally been mentioned in the literature. The pathogenesis is unknown, but the majority of the authors support the concept of airway obstruction in the cells well pneumatised of temporal bone and paranasal sinuses. The authors report a case of cholesterol granuloma of the frontal sinus treated with radical surgical techniques, and they also recommend an endoscopic approach to frontal sinus to restore or enlarge the nose-frontal canal and promote drainage and ventilation of the frontal sinus.