Diffuse histiocytic lymphoma after histologic conversion: a poor prognostic variant.

Diffuse histiocytic lymphoma (DHL) developed in 14 patients with a different non-Hodgkin's lymphoma and one with chronic lymphocytic leukemia. The median time from the diagnosis of the first malignancy to the appearance of DHL was 47 months (range, 8--112). The most common presentation of histologic conversion was new or recurrent lymphadenopathy. Hypercalcemia was associated with the onset of the DHL in four of 15 patients. Eight patients with DHL after histologic conversion were treated with doxorubicin, vincristine, and prednisone with or without cyclophosphamide, but none achieved complete remission. Two other patients did achieve a complete response with therapy (one with radiotherapy and one with cyclophosphamide, vincristine, procarbazine, and prednisone), but they had brief remissions, and no patient in this study achieved long-term, disease-free survival. This was reflected in the short (12-month) median survival after histologic transformation to DHL. It appears that patients with DHL after histologic conversion have a worse prognosis than those with de novo DHL.