[Detection of DDIT3 gene rearrangement in myxoid liposarcoma using fluorescence in situ hybridization: its clinical application and cryptic signals].

内容摘要

Objective: To investigate the clinical application of DDIT3 gene rearrangement using fluorescence in situ hybridization (FISH) in myxoid liposarcoma (MLPS) and to analyze the cases with atypical signal pattern. Methods: A total of 386 cases were examined for DDIT3 gene rearrangement using FISH in the West China Hospital, Sichuan University, Chengdu, China from January 2018 to December 2024. The clinicopathologic data and molecular detection results were collected. Six MLPS with DDIT3 cryptic rearrangement (CR-MLPS) were identified and subject to FISH testing of FUS and EWSR1 break, EWSR1::DDIT3 and FUS::DDIT3 fusion, next-generation sequencing (NGS), reverse-transcriptase polymerase chain reaction and Sanger sequencing. Results: Among the 386 successfully tested cases, 154 cases were histologically diagnosed as MLPS, of which 148 (148/156, 96.1%) were positive for DDIT3 gene rearrangements. In the positive cases, 57 cases were further subject to FUS and EWSR1 break-apart examination. Among them, 51 cases (51/57, 89.5%) showed FUS rearrangements, 5 cases (5/57, 8.8%) displayed EWSR1 rearrangements and 1 case was negative for FUS and EWSR1 rearrangement. DDIT3 gene rearrangements were negative in 238 cases (238/386, 59%). Six CR-MLPS were identified, including two females and four males, with an average age of 32 (14, 55) years, all located in the deep soft tissues of the extremities. All six cases of CR-MLPS presented typical MLPS morphology, with nodular distribution, abundant mucin, and visible branched capillaries. The cells were round and of medium size. Adipoblasts and cells with adipocyte-differentiation were also observed. The tumor cells in all six cases of CR-MLPS were negative or focally positive for S-100, and negative for p63 (4/4) and CDK4 (3/3). The Ki-67 index was 10% to 15%. Three of the six DDIT3 CR-MLPS showed small gap of DDIT3 break, one case revealed centromeric amplifications of DDIT3 gene, and two cases displayed 1 to 3 yellow/fusion signals. Subsequent FISH fusion test, reverse-transcriptase polymerase chain reaction and NGS confirmed that four cases had EWSR1::DDIT3 variants and two cases had FUS::DDIT3 variants. All six patients underwent surgical resection followed by radiotherapy. Among them, one patient had a recurrence 4 years after surgery, and another had recurrence and metastasis. Conclusions: FISH detection of DDIT3 gene rearrangements is important for the diagnosis of MLPS, whereas a small number of cases may still be missed due to cryptic rearrangement. The CR-MLPS cases present typical morphology, among which the EWSR1::DDIT3 variants are more commonly detected than the others. 目的： 探讨荧光原位杂交（FISH）检测黏液样脂肪肉瘤（MLPS）DDIT3基因易位的临床应用价值并总结其中6例DDIT3隐匿性易位MLPS（CR-MLPS）的临床病理及分子遗传学特征。 方法： 收集四川大学华西医院2018年1月至2024年12月行DDIT3基因FISH检测的386例样本的临床病理信息和分子检测结果。其中6例DDIT3 FISH检测显示阴性，形态符合经典MLPS的病例加做FUS和EWSR1分离、EWSR1：：DDIT3、FUS：：DDIT3融合FISH检测，二代测序、逆转录聚合酶链反应（RT-PCR）进一步验证，总结其临床病理特征，并复习相关文献。 结果： 386例检测病例中，154例诊断为MLPS，其中DDIT3阳性病例148例，检出率96.1%。DDIT3阳性病例中，57例加做FUS和EWSR1基因易位，检出51例（51/57，89.5%）FUS易位，5例（5/57，8.8%）EWSR1易位，另1例未检出FUS和EWSR1基因易位。238例DDIT3阴性病例中，检出6例（6/238，2.5%）DDIT3 CR-MLPS，包括2例女性、4例男性，年龄32（14，55）岁，均位于四肢深部软组织。6例CR-MLPS具典型MLPS形态，呈结节状分布，富含黏液，可见分支状毛细血管。细胞呈圆形，中等大小，并见脂肪母细胞和脂肪分化细胞。肿瘤细胞S-100蛋白阴性或局灶阳性，p63（4/4）、CDK4（3/3）阴性表达。Ki-67阳性指数10%~15%。FISH检测显示3例（3/6）DDIT3呈不典型分离信号，1例（1/6）DDIT3着丝粒扩增，2例（2/6）DDIT3基因拷贝数增多。经验证4例（4/6）为EWSR1：：DDIT3融合，2例（2/6）为FUS：：DDIT3融合。6例患者均行手术切除后放疗，1例手术切除后4年复发，1例复发并转移。 结论： FISH法检测DDIT3基因易位对黏液样脂肪肉瘤的诊断具有重要价值，但仍有小部分病例因为隐匿性易位而漏检。隐匿性易位病例具有典型的黏液样脂肪肉瘤形态，其中EWSR1：：DDIT3融合亚型更为常见。.