Neurotrophic Receptor Tyrosine Kinase 2 (NTRK2) Alterations in Low-Grade Gliomas: Report of a Novel Gene Fusion Partner in a Pilocytic Astrocytoma and Review of the Literature

Figure 1

Pilocytic astrocytoma radiographic and histopathologic features. Brain magnetic resonance imaging demonstrates T2/FLAIR curvilinear hyperintensity (a) and T1 hypointensity (b) without contrast enhancement (c). Hematoxylin and eosin-stained intraoperative cytological smear preparation (d) and frozen section (e) demonstrating an astrocytoma with thin elongated piloid (“hair-like”) cellular processes (scale microns). (f) Permanent sections showed a piloid astrocytoma with compact areas and adjacent slightly looser areas (scale microns). (g) The astrocytic nuclei have mild pleomorphism and are elongated, slightly irregular, and hyperchromatic (scale microns). (h) Abundant eosinophilic granular bodies are found throughout the astrocytoma (scale microns). (i) The Ki-67 proliferative index is low (<1%) overall (scale microns).

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