亚甲基蓝是皮肤下发生的一种罕见的恶性黑色素瘤。亚甲基蓝是一种指甲下的黑素瘤，属于肢端黑素瘤类型。亚甲基蓝是一种侵袭性较强的皮肤黑素瘤，在亚洲患者中最为常见。最近的研究表明，亚甲基蓝和肢端黑素瘤可能具有不同的分子特征。黑色素瘤的治疗依赖于临床和分子数据的分析。因此，亚甲基蓝在临床和分子特征的建立中尤为重要，尤其是在转移过程中。为了确定亚甲基蓝的突变特征并将其与肢端黑素瘤进行比较，我们对亚甲基蓝和肢端黑素瘤患者的原发和转移性肿瘤进行了下一代测序。指甲下位置比肢端位置更能作为独立的预后因子，对于整体生存有更好的预测（p = 0.001）。亚甲基蓝中最常见的基因型为三倍野生型（75%），其主要驱动基因为GNAQ（58%）和KIT（25%）突变，而肢端黑素瘤患者则有BRAF（28.6%）和RAF（14.3%）等分子型突变。亚甲基蓝中单核苷酸变异（SNVs）比肢端黑素瘤更常见，而拷贝数改变（CNAs）则更常见于转移性肢端黑素瘤。亚甲基蓝和肢端黑素瘤患者的转移性肿瘤均表现出CNAs的增加（分别为43%和80%），但SNVs没有明显增加。CNAs在转移过程中的数量有所增加。与肢端黑素瘤相比，亚甲基蓝具有独特的临床和分子特征。

Subungual melanoma (SUM) is a rare type of malignant melanoma that arises beneath the nails. SUM is categorized as a type of acral melanoma (AM), which occurs on the hands and feet. SUM is an aggressive type of cutaneous melanoma that is most common among Asian patients. Recent studies reveal that SUM and AM might have different molecular characteristics. Treatment of melanoma relies on analysis of both clinical and molecular data. Therefore, the clinical and molecular characteristics of SUM need to be established, especially during metastasis. To define the mutation profiles of SUM and compare them with those of AM, we performed next-generation sequencing of primary and metastatic tumors of SUM and AM patients. Subungual location was a better independent prognostic factor than acral location for better overall survival (p = 0.001). Patients with SUM most commonly had the triple wild-type (75%) driven by GNAQ (58%) and KIT (25%) mutations, whereas patients with AM had BRAF (28.6%) and RAF (14.3%) molecular types of mutations. Single-nucleotide variations (SNVs) were more common in SUM than in AM, whereas copy number alterations (CNAs) were more common metastatic lesions of AM. Metastatic tumors in patients with SUM and AM showed increases in CNAs (43% and 80%, respectively), but not in SNVs. The number of CNAs increased during metastasis. When compared with AM, SUM has distinct clinical and molecular characteristics.