IDH1 mutations, NTRK2, MYB, and MYBL1 rearrangements, and ATRX loss: Among patients with pilocytic or pilomyxoid astrocytomas who had testing for IDH1 mutations (n = 15), rearrangements of NTRK2 (n = 9), MYB (n = 10), or MYBL1 (n = 7), and ATRX loss (n = 10) performed on both paired surgical specimens, results remained negative in all paired samples, with no acquisitions or losses, including after systemic therapy or irradiation (Table 2). Here, ATRX is linked to pilomyxoid astrocytoma.