伴t（5；12）（q33；p13）髓系肿瘤四例报告并文献复习

The study of 4 cases of myeloid neoplasm with t （5;12） （q33;p13） and the literatures review

目的分析伴有t（5；12）/ETV6-PDGFRβ异常髓系肿瘤的临床和实验室特点。方法采用骨髓细胞短期培养法制备染色体标本，R显带技术进行染色体核型分析；采用PDGFRβ双色断裂重排探针和荧光原位杂交（FISH）技术检测该基因重排；应用多重RT-PCR技术检测ETV6-PDGFRβ融合基因，并对其中1例PCR产物进行测序分析；应用流式细胞术进行免疫分型分析；4例患者均接受伊马替尼治疗，随访治疗结果和生存期。结果4例患者中3例为骨髓增殖性肿瘤（MPN），1例为急性髓系白血病（AML）-M2。核型分析3例t（5；12）（q33；p13）为原发性异常，1例t（5；12）（q33；p13）为继发性异常，并经FISH证实为PDGFRβ基因重排；多重RT-PCR检测结果显示ETV6-PDGFRβ融合基因阳性，BCR-ABL融合基因阴性；免疫分型结果显示4例患者骨髓标本均有CD13、CD33和CD34表达；伊马替尼治疗后，其中2例患者获分子学缓解，1例获血液学和完全细胞遗传学缓解，1例在伊马替尼治疗后，ETV6-PDGFRβ融合基因短暂转阴，由于与AML相关的原发性异常的存在，使得病情迅速恶化、死亡。结论伴t（5；12）/ETV6-PDGFRβ髓系肿瘤较少见，具有独特的临床和实验室特点。t（5；12）在MPN中多为原发性异常，患者伊马替尼治疗效果颇佳，预后良好，而在AML中可能多为继发性异常，预后尚不明确。FISH技术是检测PDGFRβ基因重排的可靠手段。

Objective To report clinical and laboratory features of 4 cases of myeloid neoplasm with t（5;12） （q33;p13）. Methods Cytogenetic examination of bone marrow cells obtained from patients was performed by 24 h culture method. R banding technical was used for karyotype analysis. PDGFRβ gene rearrangement was detected by FISH using dual color break apart PDGFRβ probe. ETV6-PDGFRβ fusion genes were detected by multiple-reverse transcription polymerase chain reaction （RT-PCR）. Direct sequencing analysis was performed on the PCR products in case 1. Immunophenotype analysis was carried out by flow cytometry. Four cases were treated with imatinib （IM） and followed up. Results The diagnoses included 3 MPN and 1 AML-M2. The t（5;12）（q33;pl3） was a primary abnormality in 3 cases of MPN and a secondary abnormality in 1 case of AML-M2. PDGFRβ gene rearrangement and ETV6- PDGFRβ fusion genes were detected by FISH and multiple-RT-PCR in 4 cases, respectively. The immunophenotypical analysis of leukemia cells showed positive for CD13, CD33 and CD34. Two cases obtained MMR after the treatment of IM, one case complete hematologic and complete cytogenetic response. ETV6-PDGFRβ was negative detected by multiple-RT-PCR after the treatment of IM, but relapsed and died soon in case 4. Conclusions The t（5;12） myeloid neoplasm was a subtype with unique features. The t（5;12） maybe a primary chromosome abnormality in MPN and a secondary in AML. MPN with t（5;12） could benefit from IM, but not for AML. Dual-FISH was a reliable tool for detecting PDGFRβ rearrangement.