Epithelial-Myoepithelial Carcinoma: Frequent Morphologic and Molecular Evidence of Preexisting Pleomorphic Adenoma, Common HRAS Mutations in PLAG1-intact and HMGA2-intact Cases, and Occasional TP53, FBXW7, and SMARCB1 Alterations

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Am J Surg Pathol. 2018 Jan;42(1):18-27. 

Epithelial-Myoepithelial Carcinoma: Frequent Morphologic and Molecular Evidence of Preexisting Pleomorphic Adenoma, Common HRAS Mutations in PLAG1-intact and HMGA2-intact Cases, and Occasional TP53, FBXW7, and SMARCB1 Alterations in High-grade Cases

Abstract: We hypothesized that there is a relationship between the preexisting pleomorphic adenoma [PA]), histologic grade of epithelial-myoepithelial carcinomas (EMCAs), and genetic alterations. EMCAs (n = 39) were analyzed for morphologic and molecular evidence of preexisting PA (PLAG1, HMGA2 status by fluorescence in situ hybridization, FISH, and FGFR1-PLAG1 fusion by next-generation sequencing, NGS). Twenty-three EMCAs were further analyzed by NGS for mutations and copy number variation in 50 cancer-related genes. On the basis of combined morphologic and molecular evidence of PA, the following subsets of EMCA emerged: (a) EMCAs with morphologic evidence of preexisting PA, but intact PLAG1 and HMGA2 (12/39, 31%), (b) Carcinomas with PLAG1 alterations (9/39, 23%), or (c) HMGA2 alterations (10/39, 26%), and (d) de novo carcinomas, without morphologic or molecular evidence of PA (8/39, 21%). Twelve highgrade EMCAs (12/39, 31%) occurred across all subsets. The median disease-free survival was 80 months (95% confidence interval, 77-84 mo). Disease-free survival and other clinicopathologic parameters did not differ by the above defined subsets. HRAS mutations were more common in EMCAs with intact PLAG1 and HMGA2 (7/9 vs. 1/14, P <0.001). Other genetic abnormalities (TP53 [n =2], FBXW7 [n =1], SMARCB1 deletion [n =1]) were seen only in high-grade EMCAs with intact PLAG1 and HMGA2. We conclude that most EMCAs arose ex PA (31/39, 80%) and the genetic profile of EMCA varies with the absence or presence of preexisting PA and its cytogenetic signature. Progression to higher grade EMCA with intact PLAG1 and HMGA2 correlates with the presence of TP53, FBXW7 mutations, or SMARCB1 deletion.

上皮-肌上皮癌：存在多形性腺瘤的形态学及分子证据，PLAG1和HMGA2完整病例中常见的HRAS突变，以及高级别病例中偶现的TP53，FBXW7和SMARCB1

摘要：我们假设多形性腺瘤、上皮-肌上皮癌的组织学分级及其基因改变之间存在某种联系。本文对39例上皮-肌上皮癌存在多形性腺瘤的形态学及分子证据进行分析，如FISH检测PLAG1、HMGA2的状态及NGS检测FGFR1-PLAG1融合。还对23例上皮-肌上皮癌进行NGS检测50个癌症相关基因突变及拷贝数变异。基于多形性腺瘤的形态及分子依据，将上皮-肌上皮癌分为以下几类：(a)具有多形性腺瘤形态的上皮-肌上皮癌，但PLAG1、HMGA2无突变(12/39, 31%)；(b)上皮-肌上皮癌伴有PLAG1改变(9/39, 23%)；(c)上皮-肌上皮癌伴有HMGA2改变(10/39, 26%)；(d)原发性上皮-肌上皮癌，无多形性腺瘤形态及分子依据(8/39, 21%)。12例高级别上皮-肌上皮癌(12/39, 31%)出现以上各个类型。上皮-肌上皮癌的平均无病生存期为80个月（95%可信区间，77-84个月）。以上几个类型在无病生存期、其他临床病理参数无显著差异。PLAG1、HMGA2无突变的上皮-肌上皮癌病例更常发生HRAS突变(7/9 vs. 1/14, P <0.001)。其他的基因异常（TP53 [n =2], FBXW7 [n =1], SMARCB1 缺失 [n =1]）仅存在于PLAG1、HMGA2无突变的高级别上皮-肌上皮癌中。结论：大部分上皮-肌上皮癌由多形性腺瘤发展而来(31/39, 80%)，上皮-肌上皮癌的分子特征与多形性腺瘤的存在与否相关。PLAG1、HMGA2无突变的高级别上皮-肌上皮癌的预后与TP53、FBXW7突变及SMARCB1缺失相关。（翻译：吴建锋）