(A, B, and C) Serial sections from a reactive lymph node with non-neoplastic T-cell proliferation. In the interfollicular area, where almost all cells, including large cells (arrow), are positive for CD3 antigen (A), some CD30⁺ (B) large lymphocytes are present. (C) Coexpression of BCL-6 protein (nuclear, blue) is observed in a large CD30⁺ (cytoplasmic and membranous, reddish) cell, as detected by two-color staining (see Materials and Methods). Individual cells expressing either BCL-6 or CD30 are also seen. (A and B) APAAP immunostaining, hematoxylin counterstain, original magnification ×400; (C) frozen section, original magnification ×400.