Primary cutaneous marginal IgG4 lymphoma and Rosai-Dorfman's disease coexisting in several lesions of the same patient.

We report the unique association of primary cutaneous marginal zone B-cell lymphoma and Rosai-Dorfman disease (RDD)-type histiocytic infiltrates involving the same lesions. The patient was an 82-year-old woman with 3 long-standing, well-circumscribed firm erythematous to brownish plaques on her left arm, right scapular area, and lumbosacral area. Histopathologic examination disclosed a dermal and subcutaneous nodular lymphoplasmacytic infiltrate with evidence of germinal center colonization and light-chain restriction and sheets of S-100 CD68-positive histiocytes with ample pale cytoplasm and occasional emperipolesis of lymphocytes. The neoplastic plasma cells expressed immunoglobulin (Ig) G4. A review of 14 examples of cutaneous RDD showed a substantial number of IgG4-positive cells in only 3 of them, and a review of 8 primary cutaneous marginal zone B-cell lymphomas disclosed only 2 with significant IgG4 expression. The coexistence of lymphomas and RDD has been rarely reported in the literature but only seldom involving the same lymph node and-to the best of our knowledge-never in the skin.