Background: In contrast to cutaneous T-cell lymphoma, primary cutaneous B-cell lymphomas (pCBCL) are rare in Japan. Thus there have been no reports in the English literature that analyze Japanese pCBCL cases in detail. Objective: We describe three additional Japanese cases of pCBCL and review the Japanese literature to compare their clinical features and prognoses with those in cases that involve white persons. Methods: In our three cases, we performed immunohistochemical and flow cytometric analyses to determine the phenotypes of tumor cells. Genotypic analysis was also conducted by Southern blotting. In addition, we reviewed 43 cases of pCBCL reported in Japan. Results: In our three cases of pCBCL, the lack of systemic involvement indicated that they were primary cutaneous tumors. One of our cases, which had a poor prognosis, lacked both HLA-DR and CD44 phenotypes, which are usually observed in the diffuse large-cell type of pCBCL. We found three major differences between the reported Japanese cases including ours and the cases that involved white persons: (1) histologically, the diffuse type was presented in 79% of lesions of less than 12 months' duration in the Japanese cases but in only 9% of lesions in white persons; (2) chemotherapy was more frequently selected in the Japanese cases (51%), whereas radiotherapy was used more frequently in white cases (71%); and (3) the death rate from pCBCL was much higher in Japanese (16%) than in white (2%) persons. Conclusion: pCBCL in Japanese persons seems to be different from that in white persons in frequency, in histoarchitectural growth pattern, and in prognosis.
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