The development of more than one histologic type of lymphoma in the same patient is frequent and confers a worse prognosis.

BACKGROUND AND OBJECTIVES Distinct types of lymphoma may develop in the same patient either simultaneously or sequentially. The frequency and clinical significance of this phenomenon are still only partially known. DESIGN AND METHODS We conducted a retrospective analysis of all cases of lymphomas of different histology occurring in the same patient, denoting these cases as multiple histology lymphoma (MHL). The clinicopathologic characteristics of these cases were compared with those of cases with a single histology (SHL). The histologic classifications were made according to the REAL classification by the same pathologists throughout the study period. RESULTS MHL were identified in 46 of 347 (13%) consecutive cases of lymphoma diagnosed at a single institution. They presented more frequently in stage III-IV (p=0.008), but the age, sex, and IPI score of patients with MHL did not differ from those of patients with SHL. Small lymphocytic/lymphoplasmacytic subtype was more frequent (16.1% vs 3%, p<0.0001) and Hodgkin's lymphoma (4% vs 16%; p=0.004) less frequent in MHL. Response rates to treatment were similar (85% vs 77.5%), whereas 5-year overall survival was significantly lower for MHL than for SHL (31% vs 67%; p=0.015). Among MHL, 14 cases were diagnosed simultaneously and 32 sequentially, after a median of 18 months. The two subgroups with simultaneous and sequential presentation did not differ in their demographic, clinicopathologic or prognostic characteristics. INTERPRETATION AND CONCLUSIONS Lymphomas of different histology develop frequently in the same patient, either simultaneously or sequentially. Patients with MHL form a subgroup with few peculiar presenting clinicopathologic features but a markedly worse prognosis, thus warranting prospective biological and clinical studies.