Immunostaining of cytocentrifuged cell lines and paraffin-embedded normal tissues for NPM (APAAP technique). Cell lines: The t(2;5)-positive cell line Karpas 299 (a) and a murine mastocytoma cell line (b) both show labeling of nucleoli with antibody to the C-terminal portion of NPM (antibody NPMc). Note the cytoplasmic labeling of a mitotic cell in (b). Kidney: (a) Many cells show nuclear labeling for nucleophosmin. (b) and (c) show high power views of, respectively, a glomerulus and tubular epithelium (antibody NA24). Thymus: Two different anti-NPM antibodies give essentially identical labeling patterns of cell nuclei in a Hassall’s corpuscle and in the surrounding medullary tissue. Tonsil: Nuclear labeling of lymphoid cells is seen. The arrows in the low power view (left) indicate scattered mitotic cells in which there is cytoplasmic labeling, seen at high power on the right (antibody NA24). Cerebral cortex: Neural cells show strong cytoplasmic staining, seen at low power (above) and high power (below) (antibody NA24).