Recognizes a formalin-resistant epitope in both the 80 kDa NPM-ALK chimeric and the 200 kDa normal human ALK proteins (1). Normal ALK protein expression is restricted to the central nervous system. The hybrid gene, NPM-ALK
, created by the t(2;5)(p23;q35) chromosomal translocation encodes part of the nucleolar phosphoprotein, nucleophosmin (NPM), joined to the cytoplasmic portion of the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase (2). This antibody is a useful aid for classification of anaplastic large cell lymphoma (ALCL).