Coexistence of Langerhans cell histiocytosis, Rosai-Dorfman disease and splenic lymphoma with fatal outcome after rapid development of histiocytic sarcoma of the liver.

The coexistence of skin-limited Langerhans cell histiocytosis (LCH) and Rosai-Dorfman disease (RDD) is an exceptional finding. The association of lymphomas and histiocytosis is also infrequent. We report the case of a 68-year-old man which presented an exceptional association of cutaneous LCH and RDD and splenic marginal zone lymphoma. He was stable for few years. Suddenly, the patient was admitted into Hematology Department with a remarkable enlargement of spleen and liver without enlargement of lymphadenopathies or skin lesions flare. He died 24 h later despite treatment with systemic chemotherapy combined with prednisone. Pre-mortem biopsy showed infiltration with histiocytic sarcoma. We think that a transdifferentiation phenomenon could explain our case, although we could not show a clonal relationship between the cutaneous and the liver diseases. We also want to pay attention to the fact that a fast transformation to a more aggressive disease can occur long time after the presentation of the first lesion, a problem that stresses the importance of performing a close and permanent follow-up of these patients.