Fig. 2

Hematoxylin and eosin (HE) and immunohistochemical stains of a thick needle biopsy demonstrate a dense infiltrate of CD1a and CD207 positive histiocytes with variable S100 expression (A). Immunohistochemical analysis of lesional tissue obtained at surgical debridement shows CD207 positive histiocytes and multinucleated giant cells (B). Histopathological analysis of a biopsy taken at time of disease progression demonstrates CD1a and CD207 positive histiocytes, indicative of active LCH, with frequent nuclear indentations and rare mitoses—one of which is shown (C)