Histopathologic features of PBL. (A) This high magnification shows the cytologic features of a case of PBL in an HIV-positive patient. It displays large cells with an immunoblastic appearance, with central oval nuclei with prominent nucleoli and moderately abundant cytoplasm. (B) Cytologic features of a case of PBL in an HIV-negative patient with extranodal involvement away from the oral mucosa show plasmacytic plasmablasts with abundant bluish cytoplasm, paranuclear hof, and large nuclei. Hematoxylin and eosin stain; magnification, ×1000).