]> 2026-07-31T07:28:02+00:00 WBR0326 0 en Langerhans cell histiocytosis The findings describe the classical presentation and workup of Langerhans cell histiocytosis characterized by diabetes insipidus, exophthalmus, and lytic bony lesions, presence of Langerhans cells on pathology, and positive staining for CD1a and S100. Electron microscopy displays characteristic Birbeck granules, which resemble tennis rackets. Schwannoma Diabetes insipidus Mastocytosis Wiskott-Aldrich syndrome Pathology A 13-year-old girl presents to the physician's office for excessive thirst, frequent urination, and weight loss. She reports that she recently noticed several raised scalp lesions that have been increasing in number. On physical examination, you observe extensive scalp lesions, cervical lymphadenopathy, and exophthalmus. A CT scan displays coalescent osteolytic lesions of the skull with a geographical appearance. Biopsy of the skin lesions demonstrates dermal infiltration of clustering cells, with large ovoid pink cytoplasm under light microscopy with positive immunofluorescence staining for S100 and CD1a. Electron microscopy of the sample reveals the presence of pentalaminar membranous organelles, resembling tennis rackets, near the nuclear membrane. What is the most likely diagnosis based on the findings? A Hematology 2020-10-28T00:11:37Z 2459150.5080671 WBR0326