Langerhans cell histiocytosis associated with lichen sclerosus of the vulva: case report and review of the literature.

Langerhans cell histiocytosis (LCH) is characterized by a clonal proliferation of bone marrow-derived Langerhans cells. While cutaneous involvement is relatively common, LCH restricted to the vulvar area is a rare phenomenon and can occur in different clinical settings. Occasionally, vulvar LCH heralds subsequent multi-organ involvement with an aggressive clinical course. Even cases of LCH isolated to the vulvar area can present with local recurrences despite excision and radiation. We present a case of a 68-year-old female with a 1-month history of pruritic lesions on her vulva. Physical examination showed whitish plaques with scattered nodular areas on the labia majora. A vulvar biopsy showed a background of lichen sclerosus (LS) with foci of oval to polygonal cells with moderately abundant eosinophilic cytoplasm and folded nuclei showing frequent nuclear grooves. Immunohistochemical staining showed that the cells were positive for CD1a and S-100, confirming the diagnosis of LCH. On further workup, there was no evidence of disseminated disease involving other organs. While vulvar LCH is uncommonly seen, and with only one previous case report in the literature associated in the setting of lichen sclerosus, this case illustrates the importance of recognizing this condition and ensuring proper clinical follow-up to rule out a systemic involvement.