There is a positive immunohistochemistry for the S-100 protein and CD68 marker in RDD, and a negative immunohistochemistry for CD1a, which should be distinguished from lymphoplasmacytic meningioma, plasma cell granuloma, Langerhans cell histiocytosis and Hodgkin lymphoma. This evidence concerns the gene CD1A and sinus histiocytosis with massive lymphadenopathy.