Sinonasal undifferentiated carcinoma (SNUC) is a rare, poorly defined sinonasal epithelial neoplasm from which several genetically defined entities are emerging. IDH1/2 mutations were recently identified in a subset of SNUC. However, the ideal method for the detection of these mutations remains to be established. Cases diagnosed as SNUC between 2010 and 2020 were retrieved. Immunohistochemistry was performed using IDH1/2 mutant-specific antibody MsMab-1. Quantitative real-time polymerase chain reaction (qPCR) was performed on genomic DNA extracted from formalin-fixed paraffin-embedded tissue using 2 kits to detect IDH1/2 mutations. Sanger sequencing was performed in a subset of cases. Thirty-eight cases of SNUC were identified, 18 of which showed IDH1/2 mutations by qPCR (47.4%). IDH2 R172K and R140x were most frequent, each seen in 6 cases (33.3%). Sanger sequencing identified IDH1/2 mutations in 4 out of 21 cases (19%) and did not detect mutations identified by qPCR in 7 cases. On immunohistochemistry, strong IDH positivity was present in 2 cases (5.3%), 1 of which had IDH2 mutation, while no mutation was detected in the other. Our results demonstrating IDH2 R172K and IDH2 R140x variants are a novel finding in SNUC. Immunohistochemistry and Sanger sequencing have low sensitivity for detection of IDH1/2 mutations, and qPCR-based assays may be utilized, particularly in resource-limited settings where access to sophisticated sequencing techniques are difficult.

鼻腔未分化癌 (SNUC) 是一种罕见的、定义不明确的鼻腔上皮肿瘤，其中出现了几种基因定义的实体。最近在 SNUC 的一个子集中发现了IDH1/2突变。然而，检测这些突变的理想方法仍有待建立。检索了 2010 年至 2020 年间被诊断为 SNUC 的病例。使用 IDH1/2 突变体特异性抗体 MsMab-1 进行免疫组织化学。使用 2 个试剂盒对从福尔马林固定石蜡包埋组织中提取的基因组 DNA 进行定量实时聚合酶链反应 (qPCR)，以检测IDH1/2突变。在部分病例中进行了桑格测序。确定了 38 例 SNUC 病例，其中 18 例显示qPCR 的IDH1/2突变 (47.4%)。IDH2 R172K 和 R140x 最为常见，各有 6 例（33.3%）。Sanger 测序在 21 例中的 4 例 (19%) 中发现了IDH1/2突变，在 7 例中未检测到 qPCR 发现的突变。免疫组化2例（5.3%）IDH强阳性，其中1例有IDH2突变，另一例未检测到突变。我们的结果表明IDH2 R172K 和IDH2 R140x 变体是 SNUC 中的一个新发现。免疫组化和 Sanger 测序对IDH1/2的检测灵敏度低突变和基于 qPCR 的分析可以使用，特别是在资源有限的环境中，难以获得复杂的测序技术。