Clinically relevant gene fusions from FFPE in a case of solitary fibrous tumor. (A) MRI of the spine reveals a spinal canal mass with extradural extension from T10–T12 with mass effect and compression along the spinal cord (arrowhead). Recurrent disease caused cord compression at the T12–L1 right neural foramen. (B) The tumor mass comprises sheets of highly mitotic undifferentiated cells with rich vascular stroma and extensive zones of necrosis (upper left). High-power micrograph (bottom) illustrates the cytological features of pleomorphic small round cells with ill-defined eosinophilic cytoplasm, prominent nucleoli, and numerous mitotic figures (arrow). (C) NAB2-STAT6 is the defining oncogenic fusion in SFT. The trans-activating domain of STAT6 is highlighted in red, the EGR1 binding domain of NAB2 in green. (D) The BBS9-BRAF fusion is likely oncogenic as it retains the kinase domain of BRAF (yellow) and has a truncation of the Ras binding domain. BRAF fusions are typically expressed at a lower level, and this rearrangement was detected with 16 reads.
