Increased BLyS expression with transformation from follicular to large cell NHL. Immunohistochemical analysis of BLyS expression in biopsy specimens from a patient with follicular lymphoma before (Ai, original magnification × 200; Aii, original magnification × 600) and after (Bi, original magnification × 200; Bii, original magnification × 600) transformation from follicular to large B-cell lymphoma.