Figure 4.

NF1‐associated pilocytic astrocytoma with anaplasia (PA‐A). PA‐A developing in a patient with NF1 A and loss of ATRX expression. B. ALT‐positive NF1‐associated PA‐A demonstrating large brown immunopositive telomeric foci through chromogenic in situ hybridization in >1% of cells corresponding to the ultrabright foci identified by telomere FISH indicative of ALT. C. ALT‐negative PA‐A had a tendency to have longer telomeres (brighter signals by telomere FISH) compared to internal non‐neoplastic controls (arrow) (Case 4, Telomere FISH) D.