Introduction:Low-grade oncocytic tumor (LOT) is a recently described renal neoplasm characterized by indolent clinical behavior, a small nested architecture, and distinctive immunophenotypic features. Its distinction from other eosinophilic renal tumors, such as oncocytoma, eosinophilic chromophobe renal cell carcinoma (E-chRCC), and eosinophilic vacuolated tumor (EVT), can be challenging due to overlapping features. The L1 cell adhesion molecule (L1CAM) is being increasingly recognized as a potential diagnostic marker for LOT.Aims:To evaluate the diagnostic performance of L1CAM in distinguishing LOT from morphologically and immunophenotypically similar eosinophilic renal neoplasms.Methods:A total of 54 eosinophilic renal tumors (10 LOTs, 22 oncocytomas, 18 E-chRCCs, and 4 EVTs) were retrospectively collected from five academic institutions and reclassified according to the 2022 WHO criteria. All cases underwent histopathologic review and immunohistochemical analysis for CK7, CD117, GATA3, cathepsin K, and L1CAM.Results:L1CAM showed strong membranous expression in all LOTs (100%) and was negative in oncocytoma, E-chRCC, and EVT, yielding 100% sensitivity and specificity. Traditional markers exhibited overlapping patterns among tumor types.Conclusions:Our findings confirm L1CAM as a highly sensitive and specific marker for LOT, effectively distinguishing it from other eosinophilic renal neoplasms. Incorporating L1CAM into diagnostic panels may enhance accuracy, particularly in challenging cases.
引言：低级别嗜酸细胞肿瘤是一种近期被描述的肾脏肿瘤，其临床行为惰性，呈小巢状结构，并具有独特的免疫表型特征。由于其与嗜酸细胞瘤、嗜酸性嫌色肾细胞癌和嗜酸性空泡化肿瘤等其他嗜酸性肾脏肿瘤存在特征重叠，鉴别诊断常具挑战性。L1细胞粘附分子正逐渐被认为是LOT的潜在诊断标志物。 目的：评估L1CAM在区分LOT与形态学和免疫表型相似的嗜酸性肾脏肿瘤中的诊断效能。 方法：从五家学术机构回顾性收集54例嗜酸性肾脏肿瘤（包括10例LOT、22例嗜酸细胞瘤、18例E-chRCC和4例EVT），依据2022年WHO标准重新分类。所有病例均进行组织病理学复查及CK7、CD117、GATA3、组织蛋白酶K和L1CAM的免疫组化分析。 结果：L1CAM在所有LOT病例中均显示强膜表达（100%），而在嗜酸细胞瘤、E-chRCC和EVT中均为阴性，敏感性和特异性均达100%。传统标志物在各肿瘤类型间呈现重叠表达模式。 结论：本研究证实L1CAM是诊断LOT的高敏感性和高特异性标志物，能有效区分LOT与其他嗜酸性肾脏肿瘤。将L1CAM纳入诊断组合可提高诊断准确性，尤其在疑难病例中具有重要价值。
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