(A and B) Serial sections from a reactive lymph node with non-neoplastic T-cell proliferation. Several CD30⁺ (A) and BCL-6⁺ (B) large lymphocytes are present at the margins of a germinal center (GC), although they are also seen in the perifollicular (PF ) zone. Within the GC numerous B cells stain for BCL-6 (B), whereas cells positive for CD30 are absent (A). (C) A large cell near to a GC coexpresses CD30 antigen (reddish) and BCL-6 protein (blue), as detected by two-color staining (see Materials and Methods). No coexpression by the BCL-6⁺ GC cells is detectable. (A and B) APAAP immunostaining, hematoxylin counterstain, original magnification ×250; (C) frozen section, original magnification ×400.