Blue nevi are benign, melanocytic neoplasms that show a range of clinical and morphologic patterns and include common/dendritic, cellular, and atypical cellular subtypes. Like other nevi, they most commonly occur in skin but can occasionally involve lymph nodes where they may be misinterpreted as representing metastatic melanoma. Moreover, whether benign blue nevi can metastasize to lymph nodes and their natural history and prognostic significance has been the subject of great controversy. To date, few cases of nodal blue nevi have been reported in the literature, and those reports have had limited clinical follow-up and supporting molecular data. This study sought to determine the clinical, pathologic, and molecular features of blue nevi involving lymph nodes, clarify their clinical significance, provide evidence for understanding their pathogenesis, and highlight potential pitfalls in the interpretation of lymph nodes with an ultimate aim of improving patient care. Thirteen cases of blue nevi involving lymph nodes were identified in the archives of Royal Prince Alfred Hospital, Sydney, Australia (1984-2018). A detailed assessment of the clinical and pathologic features of each case was performed, including an evaluation of all available immunohistochemical stains. Extended clinical follow-up was available for 9 patients. Droplet digital polymerase chain reaction for GNAQ Q209L, Q209P and GNA11 Q209L mutations was performed on 7 cases of blue nevi within lymph nodes together with matching cutaneous (presumed primary) blue nevi in 2 cases. All cases showed typical histologic features of blue nevi. BAP1 was retained in all cases (n=7). There were no recurrence or metastasis of blue nevus in any case on long-term clinical follow-up (n=9, median follow-up, 12 y). The majority of cases (n=5 of 7 evaluated) had GNAQ and GNA11 driver mutations. The 2 patients with a matched primary cutaneous blue nevus and regionally associated nodal blue nevus had the same GNAQ Q209L mutation in both sites in each patient. We conclude that blue nevi can involve lymph nodes and are associated with benign clinical behavior, and probably represent so-called “benign” metastasis. Awareness of these lesions is important when evaluating lymph nodes to avoid misdiagnosis as metastatic melanoma.

蓝痣是良性黑素细胞肿瘤，表现出一系列临床和形态学模式，包括常见/树突状、细胞和非典型细胞亚型。与其他痣一样，它们最常见于皮肤，但偶尔会累及淋巴结，可能会被误解为代表转移性黑色素瘤。此外，良性蓝痣是否可以转移至淋巴结及其自然史和预后意义一直存在很大争议。迄今为止，文献中报道的结节性蓝痣病例很少，而且这些报告的临床随访和支持分子数据有限。本研究旨在确定涉及淋巴结的蓝痣的临床、病理和分子特征，阐明其临床意义，为了解其发病机制提供证据，并强调淋巴结解释中的潜在陷阱，最终目的是改善患者护理。澳大利亚悉尼皇家阿尔弗雷德王子医院 (1984-2018) 的档案中发现了 13 例涉及淋巴结的蓝痣病例。对每个病例​​的临床和病理特征进行了详细评估，包括对所有可用的免疫组织化学染色的评估。对 9 名患者进行了长期临床随访。对 7 例淋巴结内蓝痣以及 2 例匹配的皮肤（假定原发性）蓝痣进行了 GNAQ Q209L、Q209P 和 GNA11 Q209L 突变的液滴数字聚合酶链反应。所有病例均表现出典型的蓝痣组织学特征。BAP1 在所有病例中均被保留 (n=7)。在长期临床随访中，任何病例均未出现蓝痣复发或转移（n=9，中位随访时间，12 年）。大多数病例（评估的 7 例中，n=5 例）具有 GNAQ 和 GNA11 驱动突变。2 名具有匹配的原发性皮肤蓝痣和区域相关性结节性蓝痣的患者，每名患者的两个部位均具有相同的 GNAQ Q209L 突变。我们的结论是，蓝痣可以累及淋巴结，并与良性临床行为相关，并且可能代表所谓的“良性”转移。在评估淋巴结时，了解这些病变很重要，以避免误诊为转移性黑色素瘤。