Kappa (A) and lambda (B) staining in a SMZL with plasmacytic differentiation demonstrates kappa light chain restricted plasma cells predominantly within the white pulp nodules (case 2, 100×). CD43 (C) and CD3 (D) from the same biphasic SMZL showing CD43 negativity in the lymphoma (case 39, 40×). Note the ring of T cells surrounding the neoplastic white pulp nodules. E. Biphasic SMZL showing IRF4/MUM1 negativity. The inset demonstrates few scattered positive lymphocytes, including some that were large (case 47, 40×, inset 500×). F. Biphasic SMZL showing diffuse IgD positivity (case 39, 40×). (immunohistochemical stains with hematoxylin counterstain)