Primary Rosai-Dorfman Disease of Bone: A Report of Two Cases

Figure 4

Histology from open biopsy of the proximal radius lesion demonstrates sheets of pale histiocytic cells in an inflammatory background (a). The histiocytes demonstrate emperipolesis (engulfment of intact lymphocytes within the cytoplasm—arrowheads). The histiocytes express S100 protein by immunohistochemistry, characteristic of Rosai-Dorfman disease (b).

(a)

(b)