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

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Abstract
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.