PLP1 and myeloid sarcoma: For the in-depth tissue classification, PLP reactivity was used to classify multiple areas into “A—fully myelinated (full)” (representing control brain tissue, normal-appearing white matter (NAWM), pre-lesion), “B—diffusely myelinated/partially demyelinated” (dirty-appearing WM (DAWM)), and “C—absent myelin/completely demyelinated” (MS lesions) (Fig. 1b, c).