BRACHIO-CERVICAL INFLAMMATORY MYOPATHY (BCIM)

Muscle fiber necrosis

H&E stain Dark muscle fiber with loss of cytoplasmic structure H&E stain Muscle fiber invaded by cells with large nuclei and abundant foamy cytoplasm H&E stain Collapsed muscle fiber largely replaced by cells CD68 stain Muscle fiber necrosis with CD68+ cellularity invading fiber CD68 stain Segmental muscle fiber necrosis with CD68+ cellularity CD68 stain Muscle fiber necrosis with CD68+ cellularity replacing part of a fiber

BCIM: Other occasional changes
H&E stain	Acid phosphatase stain
Chronic myopathy Varied fiber size: Small muscle fibers are rounded Increased endomysial connective tissue Scattered muscle fibers with internal nuclei	Focal invasion of a muscle fiber

BCIM: Regeneration
H&E stain	ATPase pH4.3 stain
Basophilic regenerating muscle fiber	Numerous Type 2C immature or regenerating muscle fibers
H&E stain Basophilic regenerating muscle fiber: Contains bluish cytoplasm & large nuclei

BCIM: Perivascular inflammation
H&E stain	GT stain
Perivascular inflammation	Perivascular inflammation

Cell types in perivascular inflammation

H&E stain Small dark cells with little cytoplasm surround an intermediate sized vessel CD20 stain CD20+ B-cells are a prominent component of the perivascular inflammation CD3 stain A minority of the perivascular cells stain for CD3 (T-cells) CD68 stain CD68+ macrophages are scattered through the infiltrate and in neighboring connective tissue CD31 stain CD31+ endothelial cells are present in small vessels within the region of perivascular inflammation and in the lumen of the intermediate-sized vessel

BCIM: Other inflammatory cells
CD4 stain	CD20 stain
CD4 positive mononuclear cells in   endomysial connective tissue	CD20 positive B-cells in perimysium & endomysium

CD4 stain CD4 positive mononuclear cells present in endomysium & perimysium	CD20 stain CD20 positive B-cells present in focal regions
Serial sections: B-cell foci are present in some but not all (arrow) regions of CD4 cellularity

BCIM: Complement Deposition (C5b-9; MAC)

C5b-9 stain	C5b-9 stain
BCIM muscle: CD5b-9 components of complement   are deposited in endomysial connective tissue	Control muscle: No CD5b-9 components of complement   are deposited in muscle