Fig. 4
AB tumor histology. a–d MN1-rearranged tumors: (a) Case C10 showing mild vascular sclerosis (arrows). This image depicts recurrent tumor. b Case 10. The original lesion was highly sclerotic. c Case C3 showed thin tapering process with expanded endfeet in some areas (shown) and stouter clear cells in other areas. Mild vascular sclerosis is again noted. d Case C16 demonstrating fibrillary areas and vascular sclerosis. e–g BRAFV600E-positive cases: (e) Case C12 with mild vascular sclerosis. f Case C11. A pseudonuclear inclusion is present (arrow). g Case C6. h–j Cases without known driver mutations: (h) Case 22 showing monopolar columnar-like cells and a pseudonuclear inclusion (arrow). i Case C14. An eosinophilic granular body is shown in the inset. j Case C19 demonstrating mitotic activity (arrow), free hyaline bodies (arrowhead), intracellular hyaline bodies (lower inset), and multinucleate cells (upper inset). k–l C11orf95-RELA tumors: (k) Case C1, low-grade C11orf95-RELA lesion showing AB histology and mild vascular sclerosis (arrow). l Case C30 demonstrating ependymal-like pseudorosettes and clear signet ring-like cells (inset)