Unraveling morphology, methylation profiling, and diagnostic challenges in BRAF-Mutant pediatric glial and glioneuronal tumors

- Tumors with debatable diagnoses. A–D) Case 29: temporal lobe mass in a three-year-old boy. A) Neoplastic cells with round and elongated nuclei and many EGBs. B, C) Many dysmorphic ganglion cells with binucleated form in (C). D) Diffusely positive GFAP in the background, but negative in dysmorphic ganglion cells. E–F) Case 31: cerebellar tumor in a 3-year-old boy. E) Infiltrative components consist of elongated neoplastic cells with entrapped neurons. F) Many dysmorphic ganglion cells. Scale bars: 200 μm (A–F).

- Two cases with morphology of high-grade astrocytoma and MC of PXA. A–D) Case 34: parieto-temporal mass in a nine-year-old girl. A) Cellular component with round neoplastic cells infiltrative around entrapped nuclei. B) Two granular mitoses in the center of the field. (C) NeuN immunostain, an immunopositive subset of neoplastic nuclei, which raised the possibility of a neuronal component, but there was no clear neuronal differentiation. (D) GFAP immunostain shows a cytoplasmic rim in many neoplastic cells and the background. (E–F) Case 35: temporal lobe mass in a two-year-old boy. (E) High-cellular area with round-oval hyperchromic neoplastic cells and significant mitotic activity. (F) Many neoplastic cells with eccentric round eosinophilic cytoplasm resembling rhabdoid or epithelioid neoplastic cells. Scale bars: 200 μm (A, C, D); 100 μm (B, E, F).