Myopathological features in ASM (A, C, E, G) and DM (B, D, F, H). A: Myofiber injuries in ASM predominate in perifascicular areas (arrows) with the rounded atrophic appearance of regenerating myofibers; inflammatory infiltrates are mainly observed in perimysium and perifascicular endomysium and are associated with fragmentation of perimysium (asterisk). B: Perifascicular atrophy in DM characterized bymyofibers in peripheral regions of fascicles with a cross-sectional area substantially lower than in the rest of the fascicle(arrows). C: Myofiber NCAM expression (arrows) typically restricted to perifascular layers in ASM. D: In DM, NCAM-expressing myofibers are both perifascular (arrows) or grouped in foci (arrowheads). E, F: Diffuse myofiber reexpression of HLA-ABC in ASM (E) and DM (F), with marked perifascicular reinforcement in ASM (E). G, H: Macrophages in perimysium in the vicinity of fascicles (arrows) in ASM (G), and in perimysium (arrows) and perivascular areas (arrowhead) in DM (H). Frozen sections; hematoxylin-eosin (A, B) and immunoperoxidase technique for NCAM (C, D), HLA-ABC (E, F) and CD68 (G, H).