Differentiation of primary and secondary cutaneous B-cell lymphoma by Southern blot analysis

Malignant B-cell lymphomas represent a heterogenous group of lymphoreticular disorders that involve the skin in about 20% of reported cases. Skin involvement may be primary or secondary (ie, the result of hematogenous spread). Primary cutaneous B-cell lymphomas (PCBCLs) are thought to take a comparatively favorable course, respond readily to nonaggressive treatment, and lack evidence of extracutaneous spread. Nine primary B-cell lymphomas (7 centrocytic or centroblastic follicular, 1 immunoblastic, 1 centroblastic), three secondary (follicular) cutaneous B-cell lymphomas (SCBCLs) and two pseudolymphomas were studied. Staging revealed that bone marrow was involved only in SCBCLs. Centrocytes were detected in blood smear preparations of all SCBCLs. All lymphomas were treated with local irradiation. Patients with primary centroblastic and immunoblastic cutaneous lymphomas and those with secondary lymphomas received additional chemotherapy. Pseudolymphomas were treated by simple excision. Patients were monitored on average for 55 months. During this period, no patients with PCBCLs exhibited cutaneous relapses or hematogenous spread. In contrast, all patients with SCBCLs experienced cutaneous relapses. Peripheral blood, bone marrow, and skin samples from all patients were subjected to Southern blot analysis using a JH probe. Clonal rearrangement was found in all skin samples investigated except specimens from pseudolymphomas. Peripheral blood and bone marrow samples were positive in SCBCLs (the rearrangement pattern was different from that of the skin samples for two of the three patients), whereas it was negative in all PCBCLs and pseudolymphomas. In conclusion, Southern blot analysis of peripheral blood may be useful in differential diagnosis of PCBCLs and SCBCLs and a prognostic marker. Furthermore, these data confirm the comparatively favorable clinical course of PCBCLs and suggest that in these cases, local irradiation can be considered adequate treatment, whereas SCBCLs require additional systemic therapy.