OLIG2 and myeloid sarcoma: TG2 immunoreactivity was present in blood vessels which is a well known localization (van Strien et al., 2011c, 2015; Chrobok et al., 2019), but was virtually absent from Olig2-positive OLG lineage cells in chronic active (Figure 6E) and in remyelinating MS lesions (Figure 6F).