INTRODUCTION Fluid cytology for malignant cells is important for diagnosis and staging of malignancies. Morphological overlap between reactive mesothelial cells and adenocarcinoma poses challenges, for which many immunohistochemical markers like BerEp4 and MOC-31 have been used extensively. Claudin4 is a new marker with promising results; however, further studies are required to establish its role as a pan-carcinoma marker in serous effusions. This study aimed to determine the utility of Claudin4 in diagnosing metastatic adenocarcinoma in effusions and comparing its performance with BerEp4. METHODS Claudin4 immunohistochemistry (IHC) was performed on effusion cell blocks (n = 60) reported as positive or suspicious for metastatic adenocarcinoma on cytology over a 1-year period and was scored for intensity (0-3) and percentage of positive cells (0-4). The results were compared with BerEp4 IHC and correlated with follow-up. Ten benign effusions were included as negative controls. RESULTS Claudin4 IHC was positive in all 60 (100%) cases, irrespective of the primary site. BerEp4 IHC was positive in 58 (96.7%) fluids and negative in 2 (3.3%) cases. All 10 benign effusions were negative for Claudin4 and BerEp4. Claudin4 showed higher intensity and proportion scores as compared to BerEp4 in cases where tumor cells were predominantly singly scattered and was comparable to BerEp4 where tumor cells were arranged in groups. Sensitivity, specificity, PPV, and NPV of Claudin4 in our study was 100%. Sensitivity, specificity, PPV, and NPV of BerEP4 was 96.7%, 100%, 100%, and 83.3%, respectively. CONCLUSION Claudin4 IHC staining results were comparable to BerEp4, irrespective of the primary site, and it performed better in cases where tumor cells were predominantly scattered singly.

中文翻译：

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Claudin4 的诊断效用以及与 BerEp4 作为浆液性积液中转移性腺癌标记物的比较。

引言 恶性细胞的液体细胞学对于恶性肿瘤的诊断和分期非常重要。反应性间皮细胞和腺癌之间的形态重叠带来了挑战，许多免疫组织化学标记物（如 BerEp4 和 MOC-31）已被广泛使用。Claudin4 是一种新的标记物，具有良好的结果；然而，还需要进一步的研究来确定其作为浆液性积液中泛癌标志物的作用。本研究旨在确定 Claudin4 在诊断积液中转移性腺癌中的效用，并将其性能与 BerEp4 进行比较。方法 对一年内细胞学报告为阳性或可疑转移性腺癌的渗出细胞块 (n = 60) 进行 Claudin4 免疫组织化学 (IHC)，并对强度 (0-3) 和阳性细胞百分比 (0 -4）。结果与 BerEp4 IHC 进行比较并与随访相关。十例良性积液作为阴性对照。结果 无论原发部位如何，所有 60 例病例 (100%) 的 Claudin4 IHC 均呈阳性。BerEp4 IHC 在 58 例 (96.7%) 液体中呈阳性，在 2 例 (3.3%) 液体中呈阴性。所有 10 例良性积液的 Claudin4 和 BerEp4 均为阴性。在肿瘤细胞主要是单个分散的情况下，与 BerEp4 相比，Claudin4 显示出更高的强度和比例分数，并且与肿瘤细胞成组排列的 BerEp4 相当。我们研究中 Claudin4 的敏感性、特异性、PPV 和 NPV 均为 100%。BerEP4 的敏感性、特异性、PPV 和 NPV 分别为 96.7%、100%、100% 和 83.3%。结论 无论原发部位如何，Claudin4 IHC 染色结果与 BerEp4 相当，并且在肿瘤细胞主要分散为单个的情况下表现更好。