Contributed by Steven LaTulippe, M.D. and Kevin J. Flynn, M.D.
Contributor's Note:
Juvenile Xanthogranuloma is a benign cutaneous histiocytic proliferation initially described by Adamson in 1905. Clinically, the lesions are typically small. A recent series of 34 cases showed a bimodal age distribution, with one peak occuring at less than one year's age, and another peak in the 3rd decade. These lesions were usually single (82%) and were most frequently found in the cephalic area (52%), followed by the trunk, upper extremity, and lower extremity. The male/female ratio was 4:l.
The histology of these lesions generally shows a dense dermal infiltrate consisting of lymphocytes, histiocytes, Touton giant cells (which may be poorly formed or absent altogether), eosinophils, and neutrophils. The overlying epidermis is typically flattened. Ulceration is rare. Lymphocytic epidermotrophism is a frequent finding.
One series of nine juvenile xanthogranulomas examined the lesions for immunohistochemical staining patterns. They reported all cases having strong labelling of histiocytes and Touton giant cells with CD68 and HAMS6 (markers for tissue macrophages). All but one case showed positive staining of histiocytes and Touton giant cells for Factor Xllla (a marker of peripheral blood monocytes, macrophages, and dermal dendritic cells). Staining for S100 and CDla, on the other hand, was negative in all cases.
These lesions are currently thought to represent a reactive process in response to some as-yet-undefined stimulus. They are benign and usually involute gradually. It is crucial to distinguish juvenile xanthogranulomas from the X-histiocytoses. This can be done by immunohistochemistry. The X histiocytoses are positive for S-100 and CD1, and are generally negative for CD68, HAM56, and FXllla. In addition, electron microscopy shows characteristic Birbeck granules in the X-histiocytoses which are not present in juvenile xanthogranuloma.
There are several other processes that are contained in the differential diagnosis of juvenile xanthogranuloma. Xanthoma disseminatum is also a non-X histiocytosis, but lacks foreign body-type giant cells and eosinophils both pf which are usually present in juvenile xanthogranuloma. Papular xanthomas contain foam cells and Touton giant cells, but lack the mixed inflammatory infiltrate found in juvenile xanthogranulomas. Other considerations include spitz nevus and reticulohistiocytoma.
REFERENCES:
Contributed by Steven LaTulippe, M.D. and Kevin J. Flynn, M.D.
