X染色体内易位／TFE3融合基因相关性肾细胞癌的临床病理分析

Clinicopatholigic features of renal cell carcinoma associated with chromosome X inversion harboring gene fusions involving TFE3

目的探讨Xp11.2易位/TFE3融合基因相关性肾细胞癌中2种罕见基因亚型的临床病理学特征、免疫表型、荧光原位杂交（FISH）的特征性表现及预后。方法对2009年至2016年南京军区南京总医院收集的10例NONO－TFE3肾细胞癌和4例RBM10－TFE3肾细胞癌，分别进行光镜观察、免疫组织化学EnVision法、FISH检测、逆转录－聚合酶链反应（RT－PCR）及随访。结果NONO－TFE3肾细胞癌由比例不等的＂分泌期子宫内膜样腺体＂和片状的上皮样细胞混合组成，与透明细胞乳头状肾细胞癌有形态学交叉。RBM10－TFE3肾细胞癌中大多数出现双相结构，即上皮样细胞构成的腺管状和/或乳头状结构与小细胞区域形成的＂假菊形团样＂结构混合存在，另可见胞质空泡化、核沟和沙砾体等特点。免疫组织化学结果显示，NONO－TFE3肾细胞癌均中等至强阳性表达TFE3、CD10、肾细胞癌标志物（RCC）和PAX8，CK7、Cathepsin K、Melan A、HMB45、Ksp－cadherin、波形蛋白和CD117均阴性。RBM10－TFE3肾细胞癌强阳性表达TFE3、Cathepsin K、CD10、Ksp－cadherin、P504s、RCC、PAX8和波形蛋白，广谱细胞角蛋白（CKpan）和Melan A所有病例中均灶性阳性，TFEB、HMB45和CK7阴性，Ki－67阳性指数约3%～8%（平均约5%），且不同的组织学区域内免疫组织化学表达情况有所不同：PAX8、P504s、Ksp－cadherin在上皮样细胞区域表达，而在小细胞区域几乎不表达；上皮样细胞区域内Ki－67阳性指数高于小细胞区域。在分子方面，NONO－TFE3肾细胞癌中有6例扩增出融合基因产物，5例为NONO基因的第7号外显子和TFE3基因的第6号外显子融合，1例NONO基因的第9号外显子和TFE3基因的第5号外显子融合；4例RBM10－TFE3肾细胞癌均扩增出融合基因，融合位点为RBM10基因的第5号外显子和TFE3基因的第17号外显子。在FISH检测中，10例NONO－TFE3肾细胞癌均表现为距离固定且间隔较小的分离信号，约等于2个信号宽度；4例RBM10－TFE3肾细胞癌均显示〈1个信号宽度的异常信号（融合或者微小分离信号），均可视为阴性结果。共7例NONO－TFE3和4例RBM10－TFE3肾细胞癌获得随访资料，所有患者至今均无病生存。结论NONO－TFE3肾细胞癌和RBM10－TFE3肾细胞癌为2种罕见基因亚型，肿瘤均具有特殊的形态学特征和良好的临床预后，TFE3免疫组织化学阳性表达，但由于利用TFE3分离探针进行FISH检测时表现出模棱两可或假阴性结果，容易造成漏诊或误诊，应值得注意，PCR检测或二代测序可明确基因型。

ObjectiveTo study the clinicopathologic features, immunophenotype, characteristic FISH pattern and prognosis of renal cell carcinoma （RCC） associated with chromosome X inversion harboring gene fusions involving TFE3.MethodsTen cases of NONO-TFE3 RCC and four cases of RBM10-TFE3 RCC were investigated at Nanjing Jinling Hospital from 2009 to 2016 by clinicopathological findings, immunohistochemistry, and genetic analysis.ResultsMorphologically, the distinct pattern of secretory endometrioid subnuclear vacuolization was overlapped with clear cell papillary RCC, and often accompanied by sheets of epithelial cells in NONO-TFE3 RCC. Most cases of RBM10-TFE3 RCC presented with the biphasic feature that acinar, tubular and papillary patterns of epithelioid cells combined with sheets of small cells with ＂pseudorosette-like＂ architectures. In addition, cytoplasmic vacuolization, nuclear groove, and psammoma bodies were also observed. Immunohistochemically, all NONO-TFE3 RCC cases were immunoreactive for TFE3, CD10, RCC markers, and PAX8, and negative for CK7, Cathepsin K, Melan A, HMB45, Ksp-cadherin, vimentin, and CD117. All 4 cases of RBM10-TFE3 RCC showed moderate to strong immunoreactivity for TFE3, Cathepsin K, CD10, Ksp-cadherin, E-cadherin, P504s, RCC marker, PAX8, and vimentin but negative for TFEB, HMB45 and CK7. CKpan and Melan A were at least focally expressed. The antibody to Ki-67 showed labeling of 3%-8% （mean 5%）. There were some expression discrepancies of immunochemistry between different histological patterns. PAX8, CKpan, P504s, and Ksp-cadherin were expressed in epithelioid areas but not in small-cell areas. Ki-67 labeling index of epithelioid areas was higher than that in small-cell areas. In molecular analysis, NONO-TFE3 fusion transcripts were identified in 6 patients. The fusion points were between exon 7 of NONO and exon 6 of TFE3 in 5 patients and between exon 9 of NONO and exon 5 of TFE3 in one patient. All 4 cases of RBM10-TFE3 RCC demonstrated to have RBM10-TFE3 fusion transcripts and the fusion points were between exon 5 of TFE3 and exon 17 of RBM10. Using TFE3 break-apart FISH assay, all 10 cases of NONO-TFE3 RCC showed characteristic patterns of equivocal split signals with a distance of nearly 2 signal diameters. All 4 cases of RBM10-TFE3 RCC showed colocalized or subtle split signals with a distance of 〈1 signal diameter, which was considered as negative results. Long-term follow-up was available for 7 patients of NONO-TFE3 RCC and 4 patients of RBM10-TFE3 RCC. All patients were alive with no evidence of disease.ConclusionsTwo rare genotypes, NONO-TFE3 RCC and RBM10-TFE3 RCC, are reported in this study. Both of these two tumors show specific morphology and good prognosis, along with the positive TFE3 staining and the equivocal or false-negative TFE3 FISH results, which could be missed. PCR detection or next-generation sequencing can determine the genotype.