Table 3.

Differential diagnosis of immune-mediated glomerular lesions with fibrillar/microtubular substructure

	Special stains	Structure	Diameter, nm	Orientation	Most common glomerular distribution	Extraglomerular involvement
Amyloid	Congo red, thioflavin T [42]	Fibril	8–12	Random, nonbranching	Mesangium, subendothelial, intramembranous, subepithelial	Yes
FGN	DNAJB9 immunohistochemistry [6]	Fibril	16–24	Random, nonbranching	Mesangium, subendothelial, intramembranous, subepithelial	Rare
ITG		Microtubule, hollow core	30–50	Elongated, often parallel arrays	Mesangium, subendothelial, intramembranous, subepithelial	Rare
Cryoglobulinic glomerulonephritis	Cylindrical/annular; hollow core	30–35	Short, randomly oriented	Subendothelial, capillary lumen, mesangium	Sometimes (vascular)
Lupus nephritis		Fibrils/tubules	10–100 [43]	Fingerprint- like	mesangial, subendothelial, and/or subepithelial	Yes

FGN, fibrillary glomerulonephritis; ITG, immunotactoid glomerulopathy.