Intralymphatic Rosai-Dorfman Disease Associated With Vulvar Lymphedema: A Case Report of an Extremely Rare Phenomenon.

Sinus histiocytosis with massive lymphadenopathy, also known as Rosai-Dorfman disease (RDD), is a self-limited histiocytic disorder of unclear etiology which most commonly presents with cervical lymphadenopathy. Purely extranodal presentation of RDD is uncommon, and isolated intralymphatic/intravascular confinement of this entity has not previously been described. We report a 16-yr-old female who presented with vaginal swelling and mass-like enlargement of the right labia. The mass had been present for nearly a year without pain or tenderness. Clinically, the lesion was thought to be a Bartholin gland cyst. Following surgical resection, histologic examination demonstrated a hypocellular myxedematous stroma with a mixture of ectatic thin and thick-walled vessels within which there were numerous collections of histiocytes, lymphocytes, and plasma cells. The histopathologic differential diagnosis included localized vulvar lymphedema, a specialized genital tract neoplasm, and childhood asymmetric labium majus enlargement. The histiocytes showed occasional plasma cells and lymphocytes within their cytoplasm, consistent with emperipolesis. Immunohistochemical studies showed that the histiocytes expressed CD163 and S100, while ERG and D2-40 highlighted their intralymphatic confinement, ultimately leading to the diagnosis of intralymphatic RDD. Intralymphatic RDD may present as vulvar lymphedema and can potentially mimic other myxedematous neoplasms of the vulvovaginal region.