Eosinophilic Granuloma

**Semantic type:** Neoplastic Process

**Definition:** A clinical variant of Langerhans cell histiocytosis characterized by unifocal involvement of a bone (most often), skin, or lung. Patients are usually older children or adults usually presenting with a lytic bone lesion. The etiology is unknown. Morphologically, eosinophilic granuloma is characterized by the presence of Langerhans cells in a characteristic milieu which includes histiocytes, eosinophils, neutrophils, and small, mature lymphocytes.

**Synonyms:** - Chronic Unifocal Langerhans Cell Histiocytosis - Eosinophilic Xanthomatous Granuloma - Eosinophilic Xanthomatous Granuloma - Eosinophilic granuloma - Monostotic Langerhans Cell Histiocytosis - Unifocal Langerhans Cell Histiocytosis - Unifocal Langerhans-cell histiocytosis