Clinical usefulness and reproducibility of histologic subclassification of advanced diffuse histiocytic lymphoma.

Thirty-one patients with stage III and IV diffuse histiocytic lymphoma (DHL) were treated uniformly with cyclophosphamide, adriamycin, vincristine, and prednisone (CHOP). The patients were subclassified independently by two hematopathologists into groups with predominantly large noncleaved cells (eight patients), predominantly large cleaved cells (seven patients), a mixture of large cleaved cells and large noncleaved cells (11 patients), tumors with the characteristics of immunoblastic sarcomas (two patients) and unclassified (three patients). The concurrence rate on applying the subclassification was 85 per cent. Survival in patients with large noncleaved cells was superior to that of the other patients as a group (p less than 0.001), and to that of those with large cleaved cells (p less than 0.05) and large cleaved and large noncleaved cells (p less than 0.025). All the patients with large noncleaved cells are alive and "off" therapy without evidence of progressive disease. This histologic subclassification seems to identify a subgroup of patients with advanced diffuse histiocytic lymphoma having large noncleaved cells who have an excellent prognosis when treated with CHOP.