Figure 2.

(H&E, 200×) Histologic sections show a predominant component with often elongated tumor cells with occasional bipolar cytoplasmic processes in a myxoid background (A), in addition to a more solid, fibrillary component (B). C. (H&E, 400×) Both components showed frequent eosinophilic granular bodies. D. (pERK, 200×) Increased cytoplasmic and nuclear immunohistochemical staining for pERK is seen in tumor cells, indicative of MAPK pathway activation. Staining is comparable to that seen in a separate example of pilocytic astrocytoma with KIAA1549::BRAF fusion provided for reference (inset, 400×). Scale bars = 50 µm.