Extranodal Rosai-Dorfman disease: an uncommon cause of persistent nodule in the ear.

A 40-year-old woman presented with a nodule over the tragus of the right ear. A biopsy was initially reported as showing non-specific inflammation. In view of the persistence of the lesion, the histological material was reviewed, leading to revision of the diagnosis to Rosai-Dorfman disease, a diagnosis further confirmed by immunoreactivity of the histiocytes for S-100 protein. This case represented the extranodal form of Rosai-Dorfman disease in the absence of lymph node involvement.