Birbeck granules in cytoplasm is seen in ?
Langerhans cell histiocytosis
Hodgkin's lymphoma
Non hodgkins lymphoma
Gastrointestinal stromal tumor
Ans. is 'a' i.e., Langerhans cell histiocytosis Birbeck granules are characteristic of langerhans cell histiocytosis Tumour cells in the langerhan's 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)