The authors report a solitary mastocytoma with a solitary red infiltrated plaque on the dorsum of the right foot for 2 months. Histologically there were numerous mast cells infiltrating the dermis. Electron microscopy revealed CLCs located in phagosomes of activated macrophages as well as in the stromal tissue, close association between CLCs formation and damaged eosinophils was documented. Charcot-Leyden crystals (CLCs) have been found in many conditions associated with eosinophilia, but their occurrence in skin diseases is very rare. These occurrences showed the evidence that the formation of CLCs in a mastocytoma correlated to the individual and related to the biology of mast cells, basophils, eosinophils and macrophages. Phagosomes probably acted as the localization of CLCs formation. The pathological role of CLCs in a
mastocytoma needs further investigation.

Keywords : Mastocytoma, Electron microscopy