Lectin histochemistry of malignant tumors. I. Peanut agglutinin (PNA) receptors in follicular lymphoma and follicular hyperplasia: an immunohistochemical study.

Peanut agglutinin (PNA) receptors were studied in 37 cases of reactive follicular hyperplasia and 66 follicular lymphomas, using the unlabeled peroxidase-antiperoxidase (PAP) method on paraffin embedded material. Based on the binding sites of the lectin, positively stained cells were easily recognized as either cytoplasmic receptor-positive (CR+) or surface receptor-positive (SR+) cells. In the lymph node specimens, CR+ cells corresponded to macrophage-histiocytes and possibly dendritic reticulum cells; SR+ cells corresponded to lymphoid cells. Three categories of CR+ cells were noted: large, medium, and small. The large CR+ cells were present in most germinal centers from reactive nodes, but were virtually absent in neoplastic follicles. Varying numbers of medium and small CR+ cells were seen in reactive as well as neoplastic follicles. SR+ cells were present in both follicular lymphoma (64%) and follicular hyperplasia (19%). In neoplastic follicles, SR+ cells were distributed uniformly throughout every follicle in the node revealing no relation to the orientation of the node. In reactive follicles, however, the occurrence of SR+ cells was not only infrequent, but also focal, and was often associated with the polarity of the follicles. The uniform distribution of SR+ tumor cells produced a characteristic staining pattern of neoplastic follicles which, along with the disappearance of the large CR+ cells, would provide an additional feature useful in the differential diagnosis of neoplastic from reactive follicles.