USP18 and myeloid sarcoma: Follow-up, in situ hybridization studies in patient tissues (Additional file 2: Table S2) failed to demonstrate a significant difference in expression of the ISG15 E3 ligase HERC5 in cingulate cortex from MS patients compared to controls (MS = 0.1348 ± 0.0390; Control = 0.2428 ± 0.0740)—though a non-significant trend toward decreased expression of the ISG15 peptidase USP18 was noted (MS = 0.6811 ± 0.0977; Control = 1.2850 ± 0.3414; Additional file 8: Fig. S7).