Langerhans cell tumors are rare clonal disorders characterized by neoplastic proliferation of dendritic cells with distinctive protein expression (CD1a/langerin/S100) and ultrastructural features (Birbeck granules) with Langerhans cell histiocytosis (LCH) and Langerhans cell sarcoma (LCS) subtypes [1–3]. The gene discussed is CD1A; the disease is Langerhans cell sarcoma.