Expression of the PAX-5 (BSAP) transcription factor in neoplastic lymphoid cells.

(A) Pro-B acute lymphoblastic leukemia cells in a bone marrow biopsy specimen are selectively stained. The inset is a higher magnification, showing the irregular nuclei of PAX-5–positive leukemic cells. (B) Tumor cells of classic HD showing nuclear labeling, as well as cytoplasmic staining. Normal residual mantle zone B cells also express PAX-5 (APAAP technique in paraffin sections). Original magnification A, × 400; A inset, × 800; B, × 1000.