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M. Hasselblatt, B. Riesmeier, B. Lechtape, A. Brentrup, W. Stummer, F. K. Albert, A. Sepehrnia, H. Ebel, J. Gers and W. Paulus (2011) Neuropathology and Applied Neurobiology37, 803–806 BRAF-KIAA1549 fusion transcripts are less frequent in pilocytic astrocytomas diagnosed in adults Aim: Duplication of 7q34 resulting in generation of BRAF-KIAA1549 fusion transcripts is a characteristic event in pilocytic astrocytoma that may also aid distinction from diffuse astrocytic tumours. As data on BRAF-KIAA1549 fusion transcript status remain mainly limited to children, we aimed to examine the diagnostic value of BRAF-KIAA1549 fusion transcripts across all age groups. Methods:BRAF-KIAA1549 fusion transcript status was examined using reverse transcription polymerase chain reaction on formalin-fixed paraffin-embedded samples of 105 primary pilocytic astrocytomas [median patient age: 17 years (1–74 years)]. Results: Informative results (distinct wildtype BRAF bands detectable) were obtained in 105/124 cases (85%). Fusion transcripts were detected in 53 of cases (51%). They were more often encountered in tumours of infratentorial location [42/67 (63%) vs. 11/38 (29%)] and comprised KIAA1549-Ex16_BRAF-Ex9 (32 cases), KIAA1549-Ex15_BRAF-Ex9 (14 cases) and KIAA1549-Ex16_BRAF-Ex11 (seven cases). Fusion transcripts were present in 79% of tumours diagnosed in the first decade of life, but only in 51% of patients aged 11–20 years, 42% of patients aged 21–30 years, 30% of patients aged 31–40 years and 7% of patients older than 40 years. On multivariate logistic regression analysis, the association of fusion transcript status and age was confirmed adjusting for tumour location (P = 0.006). Conclusions: The frequency of BRAF-KIAA1549 fusion transcripts is significantly lower in adult patients with pilocytic astrocytoma, weakening the sensitivity of this specific diagnostic marker in that age group.