ALK and Langerhans cell histiocytosis: This classification was updated in 2022 under histiocyte/macrophage neoplasms to add anaplastic lymphoma kinase (ALK)-related histiocytosis and histiocytic sarcoma, besides moving LCH to be included in the distinct category "Langerhans cell neoplasms" that also includes Langerhans cell sarcoma [6].