THE VALUE OF IMMUNOHISTOCHEMISTRY
IN THE ASSESSMENT OF BONE MARROW DISORDERS

Attilio Orazi, M.D., FRCPath. and Dennis P. O'Malley, M.D.

CD56 (N-CAM) CD56 is a mouse monoclonal antibody made against a neural cell adhesion molecule from human neural tissue. It is effective by immunohistochemistry but requires a heat-induced epitope retrieval technique. It appears to work well in both formalin and B5/Zinker fixative and is effective in decalcified tissue. The CD56 antigen is present in natural killer cell lesions and it may be used to diagnose marrow involvement in large granular lymphocyte leukemias and natural killer cell malignancies. CD56 may stain non-hematopoietic malignant cells (e,g, melanoma) metastatic to the bone marrow . References Brody et al: Acute agranular CD4-positive natural killer cell leukemia. Comprehensive clinicopathologic studies including virologic and in vitro culture with inducing agents. Cancer 1995 15;75:2474-83.