Cutaneous Rosai-Dorfman disease: histopathological presentation as inflammatory pseudotumor. A literature review.

Purely cutaneous Rosai-Dorfman disease is exceptional. The disease is characterized histologically by large, proliferating histiocytes exhibiting inflammatory cells within their cytoplasm (emperipolesis). We present here a case of purely cutaneous generalized disease in which the routine histopathology was suggestive of an inflammatory pseudotumor. Positivity for S-100 protein, alpha1-antitrypsin, alpha1-antichymotrypsin, lysozyme, Mac387 and CD68 proteins, and negativity for CD1a protein confirmed the diagnosis of Rosai-Dorfman disease. The rarity of this case lies in the presence of conspicuous inflammatory pseudotumor-like histopathologic changes, masking an otherwise typical sinus histiocytosis cell infiltrate. This unusual presentation of the disease requires a high index of suspicion by clinicians and pathologists.