Purely Cutaneous Rosai-Dorfman Disease with Immunohistochemistry
A 65-year-old white male presented with a singular, 0.8 cm, and slowly growing mass on the right back for evaluation. Grossly, the lesion was a firm, dome-shaped nodule that was brownish-red in color. There was minimal erythema on the underlying skin. There was no history of trauma. The patient reported no associated systemic symptoms, such as fever, weight loss, or malaise. Lymphadenopathy was not appreciated on physical examination. Past medical history of this patient, includes hypertension, steatosis, and over 20 subcutaneous nodules scattered over the forearms, trunk, and neck, which have been surgically excised and diagnosed as lipomas after histopathologic examination. Previous radiologic studies with magnetic resonance imaging demonstrated multiple solitary mobile subcutaneous nodules of fatty tissue measuring a few centimeters in diameter. All pertinent laboratory results including complete blood count with differential and erythrocyte sedimentation rate were unremarkable.\nHistologic evaluation shows the dermis occupied by a sheet of confluent histiocytes with scattered neutrophils, lymphocytes, and plasma cells interspersed []. The histiocytes have indistinct cell borders, abundant eosinophilic cytoplasm, low nuclear to cytoplasmic ratio, round vesicular nuclei, and prominent nucleoli. Within some of the histiocytes were intact lymphocytes, plasma cells, and neutrophils that were engulfed by the histiocytes, a process called emperipolesis []. The histiocytes are positive for S-100 [] and CD (cluster of differentiation) 68 [], and negative for CD1a. The lesion did not penetrate the epidermis or the subcutaneous fat. The lesion was completely resected and follow-up reveals no recurrence or new nodules, and no signs of systemic involvement.