Table 1: Histological differences between granuloma annulare (GA) and necrobiosis lipoidica diabeticorum (NLD) (adapted & modified from Ref: 9,10)
Histological Characteristics	Granuloma annulare	Necrobiosis Lipoidica
Epidermis	Normal	Most often atrophic or acanthotic
Predilection of lesion	Mainly in superficial dermis	Mainly in deep dermis +/- subcutis
Necrobiosis	In descrete foci	Diffuse, marked and ill-defined
Palisading of histiocytes	Marked	Varied and not well identified; diffusely sparse histiocytes
Vascular changes	Absent capillary hyperplasia and perivascular lymphocytic cuffing	Variable capillary hyperplasia & occlusive vascular changes
Fibrosis	Absent	Common fibrosis plus necrosis
Giant-cells	Relatively few; Tuberculoid & sarcoidal features uncommon	Common Giant-cells and tuberculoid & sarcoidal features
Fat*	+/- (occasional)	++ (common)
Mucin**	++ (common)	+ (variable)
* Deposition of extracellular lipid droplets in necrobiotic foci (best seen with oil red O) ** Deposition of mucopolysaccharides in necrobiotic foci (best seen with Alcian blue)