Abstract
Renal cell carcinomas (RCCs) with the t(6;11)(p21;q12) chromosome translocation are low-grade RCC which often occur in young patients. They typically feature an unusual biphasic morphology characterized by nests of larger epithelioid cells surrounding intraluminal collections of smaller cells clustered around basement membrane material. The t(6;11)(p21;q12) translocation fuses the Alpha (MALAT1) gene with the TFEB transcription factor gene, resulting in upregulated expression of intact native TFEB that drives the aberrant expression of melanocytic markers which is a hallmark of this distinctive neoplasm. We now report 8 cases of RCC, which demonstrate TFEB gene amplification (6 without TFEB rearrangement, 2 with concurrent TFEB rearrangement) and demonstrate downstream consequences of TFEB overexpression. Like the unamplified t(6;11) RCC, all TFEB-amplified RCC were associated with aberrant melanocytic marker expression. However, several differences between TFEB-amplified RCC and the usual unamplified t(6;11) RCC are evident. First, TFEB-amplified RCC occurred in older patients (median age, 64.5 y) compared with unamplified t(6;11) RCC (median age, 31 y). Second, the morphology of TFEB-amplified RCC is not entirely distinctive, frequently featuring nests of high-grade epithelioid cells with eosinophilic cytoplasm associated with pseudopapillary formation and necrosis, or true papillary formations. These patterns raise the differential diagnosis of high-grade clear cell and papillary RCC. Third, TFEB and melanocytic marker expression was more variable within the TFEB-amplified RCC. TFEB protein expression by immunohistochemistry was detectable in 6 of 8 cases. While all 8 cases expressed melan-A, only 5 of 8 expressed cathepsin K and only 3 of 8 expressed HMB45. Fourth, the TFEB-amplified RCC were associated with a more aggressive clinical course; 3 of 8 cases presented with advanced stage or metastatic disease, 2 subsequently developed metastatic disease, whereas the other 3 cases had minimal/no follow-up. Our results are corroborated by scant data reported on 6 TFEB-amplified RCC in the literature, gleaned from 1 case report, 1 abstract, and 4 individual cases identified within 2 genomic studies of large cohorts of RCC. In summary, TFEB-amplified RCC represent a distinct molecular subtype of high-grade adult RCC associated with aggressive clinical behavior, variable morphology, and aberrant melanocytic marker expression.
摘要
伴t(6;11)(p21;q12)染色体易位的肾细胞癌(RCCs)是一种常发生于年轻患者的低级别RCC。肿瘤通常具有不同寻常的双相型形态学,其特征为大的上皮样细胞巢围绕着管腔内聚集的小细胞簇,且管腔周有基底膜物质围绕。t(6;11)(p21;q12)易位使Alpha(MALAT1)基因与TFEB转录因子基因融合,导致TFEB表达上调,进而驱动黑素细胞标记物异常表达,这正是该肿瘤的特征性标志。
本文作者报道8例具有TFEB基因扩增的RCC(6例无TFEB重排,2例同时伴TFEB重排),并证实了TFEB蛋白的过表达。与未扩增的t(6;11)RCC类似,所有TFEB扩增性RCC与异常表达黑素细胞标记物相关,然而TFEB扩增性RCC与常见的未扩增的t(16;11) RCC间存在几点明显差异。
首先,与未扩增的t(16;11)RCC(中位年龄31岁)相比,TFEB扩增性RCC常发生于老年患者(中位年龄64.5岁)。其次,TFEB扩增性RCC的形态并非完全与众不同,常见特征是具有嗜酸性胞质的高级别上皮样细胞巢常伴假乳头和坏死,或真性乳头。这些特点加大了高级别透明细胞型RCC与乳头状RCC的鉴别诊断难度。第三,TFEB扩增性RCC中TFEB和黑素细胞标记物的表达差异很大。8例中有6例TFEB蛋白免疫组化呈阳性表达;8例均表达melan-A,仅5例表达cathepsin K,3例表达HMB45。第四,TFEB扩增性RCC的临床过程更具有侵袭性。8例中3例就诊时已经处于晚期或伴发转移,2例随后发生转移,而其余3例随访资料较少或无。文献中报道的TFEB扩增性RCC较少,共6例;包括1例个案报道,1例摘要,以及2个大型RCC基因组研究中的4例报道,本文的结果得到了这6例的支持。
总之,TFEB扩增性RCC代表成人高级别RCC中的一种独特分子亚型,其临床行为更具侵袭性,形态学变化差异较大,且异常表达黑素细胞标记物。
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