Solitary mastocytoma of the vulva: report of a case.

A solitary mastocytoma was encountered involving the left labium majus of a 6-year-old girl. Tumor cells contained numerous cytoplasmic metachromatic granules that were immunoreactive for tryptase and CD117. As mast cells are difficult to recognize on routine stains, identification of mast cell lesions requires a high degree of suspicion. This is probably the first reported case of mastocytoma occurring in the vulva.