&;Birbeck granules&; are seen in
High-Yield Explanation
Langerhans cell histiocytosis Proliferative disorder of special type of immature dendritic cell - Langerhans cellMonoclonal and neoplastic of origin Cytogenetics - tumor cells express HLA-Dr, S-100, CD1aHistopathology - vacuolated cytoplasm with vesicular nuclei containing linear grooves or folds and Birbeck granules Electron microscopy - Birbeck granules- Penta laminar , rod-like, tubular appearance and dilated terminal end ( tennis racket appearance )Immunohistochemistry - detection of S-100 and CD1aMultifocal multisystem Langerhans cell histiocytosisCutaneous lesion - infiltrates of Langerhans cells over front & back of trunk and on scalp Hepatosplenomegaly , pulmonary lesions , lymphadenopathy , destructive osteolytic bone lesions , anaemia , thrombocytopenia , otitis media , mastoiditis Unisytem Langerhans cell histiocytosis Unifocal Affects skeletal system in older children or adults Asymptomatic Heals spontaneously or cured by local excision or irradiation Multifocal Multiple erosive bony masses Calvarial bone defects , Diabetes Insipidus and Exophthalmos - Triad of Hand Schuller Christian disease (Refer: Robbins & Cotran's - Pathologic Basis of Disease, SAE, 1st edition, Vol I-pg no: 621-623)