Mast cell distribution, activation, and phenotype in xanthoma.

Abstract

Activated mast cells enhance the uptake of mast cell-derived proteoglycan-low-density lipoprotein complexes by macrophages. We sought to investigate mast cell contribution to the pathogenesis of xanthoma. Twenty cases of xanthelasma palpebrarum and 6 cases of tuberous xanthoma lesions were analyzed using immunohistochemical staining. Xanthelasma lesions contained up to 5-fold more tryptase-stained mast cells than tuberous xanthoma lesions. Tuberous xanthoma lesions especially showed extensive staining of tryptase around mast cells and within some macrophages and foam cells. More than 99% of mast cells in xanthelasma lesions contained both tryptase and chymase. Approximately 60% of mast cells represented only tryptase in tuberous xanthoma lesions where the ratio of macrophages to tryptase-stained mast cells was extremely high (15:1) as compared with xanthelasma lesions (2:1). A change in mast cell phenotype has not been necessarily proven. Mast cells are activated under the microenvironment in which macrophages predominate rather than mast cells, which thus reflects the clinical phenotypes of xanthoma lesions.