This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Histiocytosis Xis seen in except- 
Select and explain. 
A. Hand schuller Christian disease, B. Eosinophilic granuloma, C. Letter-siwe syndrome, D. Torres syndrome
D: Torres syndrome
Answer: D: Torres syndrome 
Explanation: Ans. is 'd' i.e., Torres syndromeLangerhans cell histiocytosis (Histiocytosis X) o Histiocytosis X is characterized by proliferation of Langerhans histiocytes (tissue macrophages). o It is Subdivided into three Categories:-(i) Letterer-siwe syndrome(ii) Hand-Schuller-Christian disease(iii) Eosinophilic granuloma.o Tumor cells in each are derived from dendritic cells and express S-100, CD la and HLA-DR.o The presence of Birbeck granules in the cytoplasm is characteristic.o Under electron microscope, Birbeck granules have a pentalaminar, rod like, tubular appearance and sometimes a dilated terminal end (tennis-rachet appearance).