And for the definitive diagnosis of LCH requires biopsy which shows Characteristic Langerhans cells have reniform (‘coffee-bean’) nuclei and Birbeck granules (tennis-racket rods) on electron microscopy, Immunohistochemistry is diagnostic: lesional cells are positive for (CD1a) and Langerin (CD207) and variably (S100). This evidence concerns the gene CD1A and Langerhans cell histiocytosis.