Clinical: Asymptomatic skull lesions, Imaging: CT – osteolytic skull lesions, Pathology: CD1a+/S100 + histiocytes with eosinophils, Differential: Eosinophilic granuloma, Final Diagnosis: Unifocal cranial LCH (ICD: C96.6) The gene discussed is CD1A; the disease is Langerhans cell histiocytosis.