Abstract

Rosai-Dorfman disease is a reactive histiocytosis of unknown etiology, which often presents as massive lymphadenopathy with systemic inflammatory activation. The most common extranodal site of involvement is the skin, and cases of pure cutaneous Rosai-Dorfman (CRD) are quite rare. We present a case of CRD arising in an unusual location, on the face of a 77-year-old woman. The patient initially reported an enlarging, erythematous papule on the nasal root with overlying hemorrhagic crust. Subsequently, a shiny plaque emerged near her right eyebrow with associated peri-orbital swelling. The lesions were pruritic, but not painful, and no lymphadenopathy was present. A punch biopsy of the right eyebrow revealed a diffuse histiocytic proliferation with a background of mixed inflammation, consisting of plasma cells, lymphocytes, neutrophils, and eosinophils, extending into the subcutis. The S100-positive, CD1a-negative histiocytes exhibited prominent emperipolesis of adjacent inflammatory cells. CD3, CD20, and CD138 immunohistochemistry (IHC), along with kappa and lambda in situ hybridization studies, demonstrated a mixed lymphocytic and polytypic plasma cell background. MR and CT imaging did not reveal lymphadenopathy or additional mass lesions, which confirmed the pure cutaneous nature of the disease. Laboratory tests showed elevated serum IgG, while the other immunoglobulin levels were within normal limits. This case illustrates that timely, accurate diagnosis of CRD may spare patients from unnecessary and aggressive treatment. It is important for dermatopathologists to consider CRD on the differential for mixed inflammatory lesions and utilize IHC stains when necessary to differentiate it from more aggressive mimics like lymphoma and Langerhans cell histiocytosis.

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