CD1A and sinus histiocytosis with massive lymphadenopathy: These lesional histiocytes were positive for CD163 (Fig. 1B, × 200), S100 (Fig. 1C, × 200), cyclin D1 (Fig. 1D, × 200, red arrows show strong nuclear and weak cytoplasmic expression), and OCT2 (Fig. 1E, × 200, red arrow indicates lesional histiocytes; black arrow indicates background B-cells/plasma cells) and negative for CD1a and langerin, supporting a diagnosis of Rosai-Dorfman disease (RDD).