Types
juvenile xanthogranuloma (JXG)
adult-type xanthogranuloma (AXG)
Histologically, four main cell types (vacuolated, xanthomatized, spindle-shaped, and "oncocytic") are seen in variable proportions (from monomorphous to mixed variants) with different types of giant cells (nonspecific giant cells, foreign body giant cells, Touton giant cells, and "ground-glass" giant cells).
Giant cells are more prominent in AXG than in JXG; oncocytic cells (characterized by an eosinophilic, slightly granular cytoplasm similar to thyroid oncocytic cells) and mostly periodic acid-Schiff (PAS) negative giant cells with a ground-glass appearance are not observed in classic JXG (i.e., occurring in children < 2 years old).
Immunochemistry
Immunohistochemically, JXG and AXG give similar results: most xanthogranuloma cells label strongly with KiM1P and vimentin, while HHF35 and HAM56 stain less intensively. Factor-XIIIa (FXIIIa), KP1 (CD68), and HAM56 stain mostly in the periphery of the lesions.
Some markers give variable results: peanut agglutinin (PA), 60%; alpha-1-antitrypsin, 50%; lysozyme, 25%; LN3 (HLA-DR), < 10% of cells positive. Others were negative: S-100, MAC387 (L1 antigen), LeuM1 (CD15), desmin, smooth muscle-specific actin, and QBEND10 (CD34).
Xanthogranuloma can be separated from histological stimulants such as dermatofibroma (which is FXIIIa+, LN3+, KP1-, and PA-) and multicentric reticulohistiocytosis (which is FXIIIa-, KP1+, PA-, and HHF35-).
References
Zelger B, Cerio R, Orchard G, Wilson-Jones E. Juvenile and adult xanthogranuloma. A histological and immunohistochemical comparison. Am J Surg Pathol. 1994 Feb;18(2):126-35.PMID: 8291651