Solitary Mastocytoma of the Vulva

Solitary mastocytoma of the skin is a rare tumor. Its occurrence in the vulva is extremely rare with only few case reports in the literature. We report a solitary mastocytoma of the vulva in a 10-year-old girl. Her systemic examination was unremarkable. The clinical and histopathological features were consistent with the diagnosis of solitary mastocytoma of the vulva. The follow-up after surgical excision was uneventful. The purpose of this communication is (i) to report a case of solitary mastocytoma occurring in an unusual site, the vulva and to show that (ii) in this case age at presentation is 10 years with infancy as common age of presentation of solitary mastocytoma, and to show that (iii) in appropriate setting this should be included in the differential diagnosis of vulval swelling. 1. Introduction Mastocytoma is a localized collection of benign mast cells in the dermis. Mastocytoma usually appears as a solitary lesion. The common locations are trunk, neck, and arms [1]. The lesion appears at birth or in the first few months of life [2]. This case is described here because of age at presentation and its occurrence in unusual site, the vulva. 2. Case History A 10-year-old girl was brought to the hospital with complaints of recurrent swelling in the labium majus. She complains of itching which usually lasts for a day. The swelling has recurred four times. Except for the labial lesion, physical examination was unremarkable; no hepatosplenomegaly, lymphadenopathy, or skin rash was documented. Excision of the mass was performed. Gross was a single skin covered soft tissue measuring ？cm. Cut section was grey white. On microscopic examination, the mass was composed of a dense monomorphic infiltrate of tumor cells in the dermis and subcutaneous tissue (Figure 1). Cells were medium sized with regular nuclear contours and abundant pale blue cytoplasm (Figure 2). Mitotic activity was absent. Mature eosinophils were scattered in the lesion. A differential diagnosis of Langerhan’s cell histiocytosis and mastocytoma was considered. Cytoplasmic granules of the neoplastic cells were strongly metachromatic on Toluidine blue stain (Figure 3) and purple on Giemsa stain. The infiltrating cells were CD117 positive on immunohistochemistry (Figure 4). A diagnosis of solitary mastocytoma of vulva was made. Figure 1: H&E stain. Skin with infiltrate of mast cells in the deep dermis. Figure 2: H&E stain. Mast cells with pale blue cytoplasm and round to oval nuclei. Figure 3: Toluidine blue stain. Mast cells with purple metachromatic granules in the cytoplasm. Figure 4: CD