Pathologic features of PCNSL. (A) Diffuse, large B-cell lymphoma (DLBCL) involving the left parietal lobe and basal ganglia exhibits marked mass effect, subependymal spread, and invasion of the lateral ventricle at relapse, upon progression with HD-MTX and rituximab-based chemotherapy. (Courtesy Ray Sobel, MD, Stanford University School of Medicine). (B) DLBCL cells exhibiting an angiotropic growth pattern in a diagnostic specimen of PCNSL (hematoxylin and eosin [H&E] stain, original magnification ×100). (C) Invasive growth of DLBCL cells along the cerebral vasculature in PCNSL (H&E, original magnification ×200). (D) High expression of MYC by DLBCL cells in a diagnostic specimen of PCNSL, as demonstrated by immunohistochemistry (original magnification ×400). (Courtesy Eric Hsi, MD, Cleveland Clinic).