<prompt> A 2 year old child presents with scattered lesions in the skull. Biopsy revealed Langerhans giant cells. The most commonly associated is marker with this condition will beCD 1aCD 57CD 3CD 68  <response>: The history is suggestive of langerhans cell histiocytosis eosinophilic granuloma .The tumour cells in addition to birbeck granules express HLA -DR, S- 100 and CD1a Reference : Robbins and Cotran Pathologic basis of disease.South Asia Edition volume 1.page no. 622 