In clinical practice, CD20 depleting agents are not only approved for B cell-related cancers, but also increasingly used on- and off-label for autoimmune diseases, such as rheumatoid arthritis (RA), multiple sclerosis (MS) and systemic lupus erythematosus (SLE) (Cang et al., 2012). Here, MS4A1 is linked to myeloid sarcoma.