Fig. 2

Biopsy specimens from the right masseter muscle. Hematoxylin and eosin staining shows moderate size variation of the myofibers and endomysial and perimysial fibrosis (white arrow). There is atrophy of the myofibers, mainly at the periphery of the fascicles (black arrow), which is consistent with perifascicular atrophy (a). Patchy lymphoplasmacytic infiltration (white arrow) is noted in the stroma (b), which consists of predominantly more CD4-positive cells (c) than CD8-positive cells (d) in immunohistochemical staining. All figures are at 200-fold magnification