Leu 7 immunoreactivity as histochemical marker for paraffin-embedded neuroendocrine tumors.

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Abstract
Leu 7 (HNK-1) antigen, a marker for lymphoid cells expressing natural killer (NK) activity, was recently demonstrated in peripheral nerve fibers, normal and neoplastic neuroendocrine cells in both frozen and paraffin-embedded specimens. The present immunohistochemical study using a mouse monoclonal antibody describes the detection of Leu 7 antigen in a variety of human neuroendocrine tumors which were embedded in antigen in a variety of human neuroendocrine tumors which were embedded in paraffin for routine histopathological diagnosis. Forty-nine (71%) of 69 such tumors showed varying degrees of Leu 7 immunoreactivity. At least in the tumors of the lung and pancreas, the number of Leu-7-positive cells was intimately related to the aggressiveness of the tumors: the more malignant the tumors were, the less the number of Leu 7-positive cells was. Leu 7 antigen was also demonstrated in normal fundic gland cells, thymic epithelial cells and colloid materials in normal thyroid follicles. Leu 7 antigen is a useful histochemical marker for normal and neoplastic neuroendocrine cells in the field of endocrine pathology. Investigations on the distribution of NK cells in tissue sections with anti-Leu 7 monoclonal antibody should be carried out with careful attention ot these cross-reactions to non-lymphoid cell components.