MYBL1 and diffuse astrocytoma: FGFR1, NTRK2, MYB, and MYBL1 rearrangements: Among patients with diffuse astrocytomas who had testing for rearrangements of FGFR1 (n = 5), NTRK2 (n = 4), MYB (n = 2), or MYBL1 (n = 1) performed on both paired surgical specimens, results remained negative in all pairs, with no acquisition or loss (Table 2).