GFAP and myeloid sarcoma: Different aspects of microglial involvement (CHIT1 and sTREM2), astroglia pathology (CHI3L1 and GFAP), B-cell–related pathology (CXCL13), and neuroaxonal damage (sNfL) have been evaluated in several studies aiding in classifying MS disease activity (Table 1) (25–30).