<prompt> Birbeck granules in cytoplasm is seen in ?Langerhans cell histiocytosisHodgkins lymphomaNon hodgkins lymphomaGastrointestinal stromal tumor  <response>: Ans. is a i.e., Langerhans cell histiocytosis Birbeck granules are characteristic of langerhans cell histiocytosis Tumour cells in the langerhans cell histiocvtosis are derived from dendritic cells and express : S-100 CD1a HLA-DR These cells are characterized by the presence of birbeck granules in their cytoplasm unde he electron microscope, Birbeck granules have pentalaminar, rodlike tuular appearance and sometimes a dilated terminal end tennis-racket appearance 