CXCL13 expression in AITL. (A) High-power view of AITL lymph-node biopsy. Typical clusters of tumor cells with clear/pale cytoplasm are present. There is marked microvascular proliferation in the background (hematoxylin and eosin [H&E]). (B) The tumor cells are positive for CD3 (immunoperoxidase). (C) There is variable expression of CD10 (immunoperoxidase). (D) The tumor-cell clusters show strong cytoplasmic expression of CXCL13 with marked paranuclear enhancement (inset, immunoperoxidase). Images were visualized under an Olympus BX51 microscope equipped with UPlanFL ×40 (main panels) or ×65 (inset) objective lenses and WH 10 × 22 eyepiece (Olympus, Tokyo, Japan). Images were captured with an Olympus DP70 camera and processed with Adobe PhotoShop 7.0 software (Adobe Systems, San Jose, CA).