Lloyd Isaac E, Zhou Wenhua, Witt Benjamin L, Chadwick Barbara E
Department of Pathology and ARUP Laboratories, University of Utah.
Research & Development, ARUP Laboratories, Salt Lake City, UT.
Appl Immunohistochem Mol Morphol. 2019 Feb;27(2):107-113. doi: 10.1097/PAI.0000000000000572.
Interpretative criteria for programmed death-ligand 1 (PD-L1) immunohistochemistry (IHC) have been largely based on data from formalin-fixed, paraffin-embedded tissues, despite the fact that cytologic specimens, especially cell blocks, are often the only or most readily available tissue for testing. Unlike biopsy specimens, however, cytology sample processing methods can vary markedly. The purpose of this study was to evaluate the effects of several common preanalytic variables on PD-L1 IHC. Two cell lines with strong expression of PD-L1 (H441) and no expression (MCF7) were cultured in vitro. Harvested cells were collected in PreservCyt, CytoLyt, cell culture media (RPMI), saline, and formalin. Cell blocks were prepared by the plasma-thromboplastin method or Cellient automated system and stained with the FDA-approved 28-8 PD-L1 antibody per protocol. PD-L1 expression was scored manually by 3 pathologists for stain intensity and localization and compared across preparation methods. Several IHC staining patterns were observed: complete membranous, partial membranous, globular, and cytoplasmic, with some overlap. Cellient blocks had the best interobserver agreement and cytomorphology, highest proportion of strong complete membranous staining (82%), and least amount of cytoplasmic (11%) and globular staining (8%). RPMI, saline, and formalin samples demonstrated increased amounts of cytoplasmic and globular staining relative to Cellient, while CytoLyt exhibited the poorest performance overall. Interpretation of PD-L1 IHC on cell blocks is feasible for most processing methods examined, but may require recognition of increased cytoplasmic and globular staining in some sample types. Cellient cell blocks demonstrated superior performance compared with other methods.
程序性死亡配体1（PD-L1）免疫组织化学（IHC）的解释标准很大程度上基于来自福尔马林固定、石蜡包埋组织的数据，尽管事实上细胞学标本，尤其是细胞块，往往是唯一可用于检测的组织或最容易获得的检测组织。然而，与活检标本不同，细胞学样本的处理方法可能有显著差异。本研究的目的是评估几种常见的分析前变量对PD-L1 IHC的影响。将两种PD-L1表达强（H441）和无表达（MCF7）的细胞系进行体外培养。收获的细胞收集于PreservCyt、CytoLyt、细胞培养基（RPMI）、生理盐水和福尔马林中。通过血浆凝血酶原方法或Cellient自动化系统制备细胞块，并按照方案用FDA批准的28-8 PD-L1抗体进行染色。3名病理学家对PD-L1表达进行手动评分，评估染色强度和定位，并比较不同制备方法的结果。观察到几种IHC染色模式：完全膜性、部分膜性、球状和细胞质性，存在一些重叠。Cellient细胞块在观察者间一致性和细胞形态方面表现最佳，强完全膜性染色比例最高（82%），细胞质性染色（11%）和球状染色（8%）最少。与Cellient相比，RPMI、生理盐水和福尔马林样本的细胞质性和球状染色量增加，而CytoLyt总体表现最差。对于大多数所检测的处理方法，对细胞块进行PD-L1 IHC解释是可行的，但可能需要认识到某些样本类型中细胞质性和球状染色增加的情况。与其他方法相比，Cellient细胞块表现出卓越的性能。
